Brooke Shields & Katie Holmes: New B.F.F.s

Wednesday November 01, 2006 08:50 AM EST

Holmes (left) and Shields

ANG/Fame; Charley Gallay/London Entertainment/Splash

Despite her very public battle with Tom Cruise, when Brooke Shields met up with his fiancée, Katie Holmes, at a charity event in Pacific Palisades, Calif., Oct. 29, the two "were so lovely to each other," an onlooker tells PEOPLE in its new issue.

Perhaps that's because they go way back – to the September premiere of Grey's Anatomy, at least, which they watched together in Shields's living room. (After Cruise slammed Shields for using medication to treat her postpartum depression, he famously apologized in August.)

Coincidentally, the two new moms gave birth – Shields, 41, to her second daughter, Grier, and Holmes, 27, to daughter Suri – on the same day, April 18, and at the same L.A. hospital.

The two are "absolutely" friends, Shields told Access Hollywood at the Pacific Palisades event, which benefited Hands of Change, an employment and mentoring program for women. "You never know how life is going to bring people together."