Mark Wahlberg and Rhea Durham, his longtime partner and his wife of six months, welcomed their fourth child together on Monday evening at 6:35 pm.

The couple is reportedly on cloud nine after welcoming a daughter named Margaret Grace at Cedars Sinai Medical Center in Los Angeles, a source says.

"Mark was in the delivery room with Rhea," says the source. "And he cheered her on all the way. Rhea was a real trouper. They can't wait to get home."

"A big happy family with their four kids is what they wanted."

Congratulations to Mark Wahlberg and Rhea Durham!

Looks like they've gotten there! Rhea and Mark's three older children are Ella, 6, Michael, 4 and Brendan, 1. They all must be psyched to meet Margaret.

Mark's new film, The Lovely Bones, opens later this month.