Sylvester Stallone is Jason Statham and Rosie Huntington-Whiteley's ''baby guru''.

Jason and Rosie are currently expecting their first child together and the model, 30 and her 49-year-old fiancé have been asking his 'Expendables' co-star Sylvester, 49, for parenting advice.

A source told the Sunday Mirror: ''The chat always seems to be parenthood. It's not a sight you expect - two action heroes talking about nappy duty over a beer in the back garden.

''Rosie and Jason are so fond of Sly and he's like their baby guru.

He has said 1,000 times he'd love to babysit their child.

''They'd take him up on it too. He's one of the few people they'd feel comfortable leaving their baby with.''

Sylvester has three daughters, Sophia, 20, Sistine, 18, and Scarlet, 14, with wife Jennifer Flavin and has been giving Jason advice on how to cope with raising girls.

The insider said: ''He's warned Jason how hard it is to be a dad to girls. So it's not only advice on new-borns but teens too.

''If Jason has a snag with raising his baby, he'll probably call Sly before he Googles it.''

Stallone's first-born, son Sage - with first wife Sasha Czack - died at 36 in 2012. The pair also have son Seargeoh together.

Meanwhile, Rosie announced her pregnancy on Instagram in February.

She wrote: ''Very happy to share that Jason and I are expecting!! Lots of love Rosie x Photo by @jasonstatham''

The actress previously admitted she would love to start a family with 'Fate of the Furious' star Jason, who she got engaged to last year after six years of dating.

But she revealed she was unsure where the couple would raise their future children as they currently live in Los Angeles.

She shared: ''Having a family is something I think about for sure, and whether I'd live here in America or in England.

''But it's not always as simple as that. I have no idea what will happen, but it'll be interesting to find out, right? And nothing will be perfect, I'm sure.''