Actors Rebecca Romijn and Jerry O'Connell are having twins.

The couple, who married last July after dating for more than four years, will be welcoming the babies — two girls — during the northern hemisphere winter, a source told People.

The children — the couple's first — were conceived naturally, without the aid of fertility treatment Clomid or in vitro fertilisation, the magazine's website reported.

"Jerry couldn’t be happier about becoming a dad," a friend told Us Weekly.

"They haven't told that many people," a source told E! Online gossip columnist Mark Malkin.

"Rebecca wanted to wait until she was done shooting 'Ugly Betty'."

Already checking in with the congratulations is Rominjn's ex John Stamos.

"I'm happy for all four of them," the 'ER' and 'Full House' star told Malkin.

"I wish them the best."

The 35-year-old former fashion model best known for her role as the mutant Mystique in the 'X-Men' films, was married to Stamos for five years. After splitting in 2004, their divorce was finalised a year later.

Romijn and O'Connell, a former child star who appeared in 'Stand By Me', were first seen together in late 2004 at an Al Green concert and a deli in LA. The 34-year-old 'Jerry Maguire' actor proposed to Romijn in New York during September 2005 and were married on 15 July last year in an intimate LA ceremony.

Romijn, currently best known for her role as the transsexual Alexis on 'Ugly Betty', told Self magazine recently that she hoped to be "lucky enough" to have children.

And earlier this month O'Connell had revealed: "We're trying to get pregnant."

"It would be amazing if it happened," he told People and said that "practicing" had been "a lot of fun".