Penn Badgley's friends have been calling his son by the wrong name after a mistake on the Internet became difficult to correct.

The 'You' star is dad to a four-year-old son with his wife Domino Kirke and the couple has never publicly revealed what he's called, but the youngster has been mistakenly named online as "James" and the misunderstanding has led to family friends referring to the little boy by the wrong name.

During an appearance on 'The Tonight Show Starring Jimmy Fallon', Penn explained: "This is a very weird thing to say but our littlest who is four … His name is not James.

"The Internet, on Wikipedia, for many years, his name was James. And we'd get it removed, it would go back. His name's not James.

"And like, you know, I feel weird saying that but I just thought, well, you know what? I have a platform, why not clear the air?"

Penn added: "There are people who are close to the family who haven't seen us in a while, they send us a card and it says: 'To all of us and James'."

The actor - who is expecting twin boys with his wife and is step-father to her 16-year-old son Cassius - went on to explain they have decided not to publicly name their little boy in a bid to keep him out of the spotlight, but Penn insisted his name is "good".

He added: "His name, because he's four, will remain undisclosed for as long as we can. It's a good name though!"

Penn went on to talk about his twins who are due to arrive over the summer. He said: "It's thrilling, obviously. It's such a nice dose of reality. Like every time I see the sonogram it just … it feels so good.

"So as an only child, that's touching to see them together. They're in there like it's a hot tub. I actually have seen … there's a sonogram of them almost like facing each other.

"I cannot fathom what it would be like to have someone with you there. You know what I mean? And I'm going to be parenting them? I'm going to have to raise them! ...

"The four-year-old we have ... he's stoked because he really wants to be a big brother ... And the 16-year-old, he's excited for us but he's also like, 'I'm going to leave in two years'."