Mariah Carey and Nick Cannon's split is reportedly getting contentious.
The former couple, who separated earlier this year after six years of marriage and have three-year-old twins, Monroe and Moroccan, are trying to reach an amicable settlement before filing for divorce, but are said to be "arguing over property and custody of the twins."
A source told PEOPLE.com: "I think they're trying to work all these details out on property and the kids before it gets filed. They communicate because of the kids."
Their split has been especially difficult for the 44-year-old beauty, who was criticised for showing up too late to perform 'All I Want For Christmas Is You' at the Rockefeller Centre Christmas tree taping on Tuesday (02.12.14) because she was on the phone with her divorce lawyer "for close to five hours straight."
But the insider added: "She's trying to keep it together. She's focused on caring for her children and her upcoming five sold-out Christmas engagements in New York."
Mariah - who has yet to comment on her split from Nick - was disappointed that the lengthy call with her lawyer forced her fans to wait in the rain on Tuesday and her performance had to be rescheduled for the following day.
The source said: "She would never want to upset her fans."
'America's Got Talent' host Nick, 34, who confirmed in June that they'd been living apart for a few months, previously vowed to put their children first and was spotted visiting them at his estranged wife's New York City home for Thanksgiving last week.

Cameron Diaz says she can act like a "pretty good" singer.
The 42-year-old actress, who is in a relationship with musician Benji Madden and previously dated Justin Timberlake, wasn't worried about starring in the upcoming film adaptation of the musical 'Annie' and claims she deliberately sang out of tune in 'My Best Friend's Wedding' in 1997.
Discussing her infamous karaoke performance of 'I Just Don't Know What To Do With Myself' in the romantic comedy alongside Julia Roberts, she said: "Yeah, you know. They're two extremes. You don't really sing that bad if you can't sing at all. You know what I'm saying? It's called acting.
"That [role] is me acting like I can sing really bad and this ['Annie'] is me acting like I can sing pretty good. The truth lies somewhere in between that spectrum."
Meanwhile, Cameron relished the opportunity to take on the role of nasty Orphanage supervisor Miss Hannigan in the new movie and gave the character a modern twist.
She told 'Good Morning America': "For me, the original Miss Hannigan took place in a time where women weren't validated if they weren't married. If they didn't get married they failed.
"In today's culture, we are so focused on celebrity and this Miss Hannigan doesn't feel validated or that she's worthy of love because she lost her chance at stardom.
"She treats the kids the same way she treats herself and until she learns how to love herself, she can't become who she truly is."

Mark Wahlberg is seeking a pardon after being convicted of assault in 1988.
The 43-year-old actor - who served 45 days in jail after originally being sentenced to two years behind bars for blinding a man in one eye with a wooden stick after attempting to steal two cases of alcohol outside a convenience store in Boston - reportedly filed an application with the Massachusetts Board of Pardons last week, asking to have his conviction erased from the record because he is "not the same person."
In documents filed on November 26, the 'Ted' star, who has four children, Ella, 11, Michael, eight, Brendan, six, and Grace, four, with wife Rhea Durham, wrote: "I am deeply sorry for the actions that I took on the night of April 8, 1988, as well as for any lasting damage that I may have caused the victims.
"Since that time, I have dedicated myself to becoming a better person and citizen so that I can be a role model to my children and others."
Mark also listed several examples of his good deeds since the attack, including his work with the Mark Wahlberg Youth Foundation, according to the New England Cable News.
But he added: "I have not engaged in philanthropic efforts in order to make people forget about my past. To the contrary, I want people to remember my past so that I can serve as an example of how lives can be turned around and how people can be redeemed.
"Receiving a pardon would be a formal recognition that I am not the same person that I was on the night of April 8, 1988. It would be a formal recognition that someone like me can receive official public redemption if he devotes himself to personal improvement and a life of good works."

Megan Fox and Brian Austin Green were hit by a drunk driver last night (04.12.14).
The couple, who have sons Noah, two, and Bodhi, nine-months, narrowly escaped uninjured after a MINI Cooper smashed into their Range Rover in Los Angeles.
The 'Anger Management' actor, 41, was driving the 'Teenage Mutant Ninja Turtles' actress, 28, near Mulholland Drive at 9.30pm when the MINI, travelling in the opposite direction, crossed onto their side of the road and violently side-swiped their vehicle.
A law enforcement source told gossip website TMZ.com that the impact was enough to blow a tyre on the stars' Range Rover.
Brian, who also has son Kassius, 12, from a previous relationship with Vanessa Marcil, immediately called the police and the other driver, a 35-year-old male, was arrested at the scene, as his blood alcohol level was twice the legal limit.
None of the couple's children were with them when the incident occurred.
Earlier in the day, the pair, who tied the knot in 2010, were spotted enjoying a romantic breakfast date at the Beverly Glenn Mall in Beverly Hills.
Megan previously joked that they rarely have date nights because she doesn't want to get pregnant again.
She said: "We did that one time and we made sure I wasn't ovulating because I didn't want to get pregnant again. Sorry! Too much information. But we did that once. We go for sushi and a movie."

Demi Lovato admits she almost returned to rehab last year.
The 'Heart Attack' hitmaker, who spent three-months in treatment for bulimia, a self-harming disorder and drug abuse in late 2010, credits her longtime boyfriend, Wilmer Valderrama, 34, for helping her to avoid relapsing when he noticed she was displaying signs of an eating disorder again.
Speaking about her recovery, the 22-year-old star said: "It's been difficult. I almost went back to rehab for my eating disorder last summer. I was obsessing over food and terrified of it at the same time. Wilmer noticed and called me out on it, which was a relief."
Demi is slowly learning to enjoy a balanced diet.
She told Fitness magazine: "Now I'm on a structured meal plan. I eat four small meals and two snacks a day. It's teaching me portion control."
The former Disney star, who still works out regularly so she can be stronger "physically and mentally," insists she feels much more confident about her body these days and her new motto is: "If Beyoncé can do it, I can do it."
She added: "If she can work out, have the incredible body she has, have a kid, and be as successful as she is, then I sure as hell can, too."
Demi also looks up to the Kim Kardashian West and other celebrities that are known for their curves.
She said: "Say what you will about the Kardashians, but they've really helped make curvy bodies beautiful again. It's so nice to look around and see women with hips and a butt, like Iggy Azalea and Jennifer Lopez. They have great figures, but you know they also work really hard for them and don't try to hide their curviness."

Justin Bieber has moved into a glass mansion in Beverly Hills.
The 'Beauty and a Beat' hitmaker - who cleared his belongings from a rented condominium in the same area of Los Angeles on Monday (01.12.14) just six months after he moved in, is renting the new landmark house for almost $60,000 a month.
A source said the 20-year-old Canadian star has secured a short-term lease and his new abode has already captured the interest of architectural aficionados due to its unique design.
The lavish property is 6,537 square feet and boasts a seven car garage, six bedrooms and seven bathrooms, according to gossip website TMZ.com.
Justin's previous neighbours were relieved when he moved out of his last rental property earlier this week, as they were tired of his wild parties.
Days after moving into the building in June - in which he rented the penthouse plus an apartment below - police were called to speak to Justin amid complaints of a strong smell of marijuana.
A month later, the building hired extra security but despite that, law enforcement visited the star's home six times in just one night following complaints from neighbours.
The 'Never Say Never' singer - who is on probation for two years for egging the property of a resident in his old Calabasas neighbourhood - was also visited by Beverly Hills police twice in October when he threw a "homecoming" party.

Ryan Seacrest has reportedly split from Shayna Taylor.
The 'American Idol' host, who admitted over the summer that he eventually hopes to have a "great marriage" like his parents, has ended his relationship with the 23-year-old personal trainer and model after 18-months of dating.
But is seems the 39-year-old star may have already moved on, as he was spotted with a mystery blonde beauty at the GQ Men of the Year party in Los Angeles last night (04.12.14).
An insider told gossip website TMZ.com that Shayna was nowhere in sight because Ryan recently ended their relationship.
News of their split comes just months after friends predicted the media mogul was preparing to propose to Shayna.
A source said in July: "Everyone before Shayna bored him. He's moving fast."
Another insider said:"They are so affectionate and sweet together. He's ready to settle down. Shayna came into his life at just the right time."
Earlier this year, Ryan confessed his parents, Connie and Gary, are his relationship idols.
He said: "I look at what my mom and dad have had for 40-plus years - a fantastic relationship and great marriage. Someday I'd like that. They're my role models."

Steven Moffat says a woman will eventually play 'Doctor Who'.
The lead writer and executive producer of the BBC sci-fi series would cast a female as the titular Time Lord if the right actress came along to play the character.
Speaking to BANG Showbiz at the Sky Women in Television and Film Awards at The Hilton Hotel in London today (05.12.14), he said: "We've been laying in the possibility for an awfully long time, but you don't cast that way. I know I'm going to get in trouble for saying that - you cast a person, you don't cast the gender."
The 53-year-old showrunner is adamant the Doctor - who is currently played by Peter Capaldi - does not have to be a male, and he proved this by making villainous Time Lord The Master a woman - renamed as The Mistress and played by Michelle Gomez - for the first time.
He continued: "But we did just make the female Master, she turns up and the Doctor doesn't say anything about it, he doesn't react at all, he thinks that's perfectly normal. It's not impossible no, it is entirely down to who the best person is."
Even though a female has never played the Doctor, more women have been hired to work behind the scenes on the programme in recent years.
He said: "We've had two female directors last year and I can honestly say that Rachel Talalay gave us the most macho 'Doctor Who' we had ever had. There was a load of explosions and soldiers and shouting. They bring their brilliance whatever their individual brilliance is."
Other stars to attend the ceremony included Mary Berry, Jon Snow, Michelle Collins and Vanessa Redgrave.
Rosamund Pike won The MAC Best Performance Award but was not present as she gave birth to her second son this week, while Redgrave was honoured with The EON Lifetime Achievement Award.

Stevie Nicks never wants to get married again.
The Fleetwood Mac singer, who was married to Kim Anderson for three months in 1983, says she is happily single at the moment, and while she would consider online dating she doesn't want to walk down the aisle at any point.
The 66-year-old star - who previously dated her bandmates Lindsey Buckingham and Mick Fleetwood, and the Eagles' stars Don Henley and Joe Walsh - said: "I'm happy. I might have a relationship, but I'm never getting married again.
"Mick and I always laugh about going on Match.com together and saying, 'We're looking for somebody with no health problems. And no bunches of ex-wives and ex-husbands.' "
The 'Dreams' hitmaker admits she would like to fall in love again but if she doesn't find another partner she will still have a good life.
She said: "There is always hope. If somebody comes along and he's worth it, then it will be a lucky throw of the cards. But either way it's going to be great."
Stevie has lost 10 pounds in the last few months since the band embarked on a new tour and she credits Lady Gaga's song 'Do What U Want' for inspiring her to dance off the pounds.
She added to PEOPLE magazine: "I go onstage for three hours, four days a week and have lost about 10 pounds in the last couple of months.
"The Lady Gaga song 'Do What U Want' makes me want to dance and made me revise the hustle. My girlfriends and I used to do this [dance] at clubs 30 years ago. Now it's a great way to exercise."

Gerard Butler has moved in with Morgan Brown.
The 45-year-old actor, who started dating the interior designer earlier this year, is reportedly completely smitten with the brunette beauty and is planning to propose after just three months of dating.
A source said: "Gerard is a one-woman man now. They just moved in together. And now they're talking marriage."
The '300' star - who sought treatment in rehab in 2012 after becoming addicted to painkillers after sustaining an injury while shooting the movie 'Shattered' in 2007 - has adopted a much healthier approach in recent months in a bid to keep up with former model Morgan, 38.
The insider added to Life & Style magazine: "He says Morgan also put him on a regime of green juices, and since then, he's lost weight and he's feeling healthier."
The couple went public with their romance last month, but were first spotted kissing on a beach in California in September.
Earlier this year, Gerard complained that he was struggling to find the right woman.
During an interview in March, he said: "I have not met the one princess yet.
"That doesn't mean I have not met a lot of princesses along the way, but not the one and only yet.
"Or maybe I have and she might come back into my life at some point. You should never rule out anything. But am I seeing the one now? The answer, sadly, is no."

Bette Midler thinks Beyonce Knowles is "beyond human."
The 'Wind Beneath My Wings' singer - who recently slammed Ariana Grande for having a "silly high voice" and for wearing scantily-clad attire in her music videos - says she is a huge fan of the 33-year-old singer and loves listening to her albums.
Asked what kind of music she listens to, she said: "I like Taylor Swift, and I adore Beyoncé - she's beyond human, and strong, and a real athlete."
Despite recently criticising Ariana's voice, the 69-year-old star insisted she wouldn't ever "disparage" anyone's musical ability.
She added to Harper's Bazaar magazine: "I don't think any music is better than other music. As long as it's an expression of who you are and what you're going through, it's valid - and I don't denigrate anybody's effort."
Bette recently apologised to the 22-year-old singer after she branded the brunette beauty's music videos "silly beyond belief" and poked fun at her voice.
The 'Love Me Harder' singer was left feeling shocked by the icon's comments, but wrote on Twitter: "Bette was always a feminist who stood for women being able to do whatever the F they wanted without judgement! Not sure where that Bette went but I want that sexy mermaid back!!! always a fan no matter what my love (sic)"

Ariana Grande has adopted a new dog.
The 21-year-old singer took to her Instagram account to post a picture of her new five-month-old pet pooch Cinnamon and promised to give her latest four-legged friend lots of love and spoil her "unconditionally" after getting her from a rescue centre.
In a message attached to the picture, she wrote: "time for y'all to meet somebody very special. This is Cinnamon! She's 5 months old & is the sweetest baaaaabe. she was found in a box on the side of the street a few months ago & has been living in a rescue ever since. Now she lives with me & my other babies! She will be safe, spoiled and loved unconditionally!!!!!! absolutely shatters my heart how somebody could toss an innocent creature aside like that. nothing hurts my heart more. we love you so so much Cinnamon. welcome to the grande family my babe #adopt (sic)"
Ariana also added a picture of the cute canine lying on a fetching leopard-print bean bag.
She captioned the image: "so blessed to have found each other !!! #cinnamon #rescue #adopt #love (sic)"
Ariana has introduced Cinnamon to her other dog, Fawkes - her fourth pet pooch after Coco, Toulouse and Ophelia - and she seemed delighted that the pair are getting on well.
She posted a picture of the canines hanging out and added the caption: "cinnamon & fawkes getting acquainted last night (sic)"
Ariana also adopted Fawkes, whose full name is Fawkes Kitty, and the brunette beauty took to her Instagram account in August to introduce the four-legged friend to her friends.
She wrote: "Want to introduce y'all to somebody... this is Fawkes! I adopted her while I was in Florida last month. She is an angel! And a bad ass bitch haha. She's got the fiercest, sweetest and most daring nature! Constantly play fighting and wrestling with Toulouse even [though] she's half his size. She is so brave. I love her. (sic)"