CAMERON & NICOLE'S TWIN BABY FEVER !

CLOSE-KNIT Cameron Diaz and Nicole Richie are each another baby - and the kid-crazy sisters-inlaw are hoping to take their surrogate journeys together, tipsters dish.

"Charlie's Angels" movie beauty Cameron, 49, and hubby Benji Madden are planning for a second child, causing Nicole to crave a third with husband Joel Madden, insiders spill.

"They're always over each other's houses. It's always the four of them and the kids," a source snitches.

Former "Simple Life" reality star Nicole married Good Charlotte singer Joel in 2010 and later introduced longtime pal Cameron to her hubby's identical twin and bandmate, Benji. The screen star and the guitarist tied the knot in January 2015, and "The Mask" actress left Hollywood behind to focus on her family life!