James, who plays sex-obsessed, big talker Jay on the TV series, and Clair are both 23 and have been together for less than a year - but are delighted by the news they're going to be parents.
'Clair and I wanted to let everyone know we're having a baby,' says James.
'Chuffed to say it's going brilliantly.'
The actor and former FHM High Street Honey Clair were introduced by mutual friends last September and have been inseparable ever since.
James even took Clair with him while filming The Inbetweeners film in Magaluf earlier this year.
'All very exciting with the film out in August and baby out soon after that,' James told The Sun.
'Can't quite believe my luck. Didn't think I had it in me.'
We wish them the best of luck. But gosh they're young.
How old were you when you had your first baby?
More on Parentdish: Why being a dad at 23 is wonderful
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