Matthew Rhys only speaks Welsh to his baby son.
The ‘Americans’ actor and partner Keri Russell welcomed baby Sam into the world last May and the 42-year-old star is determined the tot will pick up his native language.
Asked if he will teach Sam to speak Welsh, he said: "I am speaking purely in Welsh to him, that’s it.
"His replies, you’d think he was speaking in Welsh as well. It’s quite a gutteral language."
Keri also has son River, nine, and daughter Willa, four, from her marriage to Shane Deary, and Matthew says they have adapted well to having a baby brother.
Speaking on ‘Live! With Kelly’, he said: "The older ones are brilliant, really good, they’ve claimed him as their own."
But the first-time father admitted he worries a lot about the baby, even though Keri always tries to put him at ease.
He said: "She’s been a reassuring hand. I’m the one going, ‘What about…’ and she goes, ‘Shut up it’s fine.’
"There was a moment recently when – I said, ‘He has a very heavy cold and we’ve got to take him to the doctor.’ She’s like, ‘He has a cold, I’m gonna get my hair blown out.’ I go, ‘I’m gonna take him to the doctor.’ She went, ‘You take him to the doctor and when the doctor tells you he has a light cold, text me.’ "
Asked whether he then texted her three minutes later, he added: "Probably less. It was more like two. It’s a cold, we’re fine!"
Keri and Matthew – who play married undercover KGB agents in ‘The Americans’ – have been extremely private about their romance and only made their first public appearance as a couple in April 2014 after dating for some time.
Matthew Rhys’ language lessons for son
