How Casper Smart Plays Dad to Jennifer Lopez's Twins

Casper Smart and Jennifer Lopez on February 26, 2012 in West Hollywood, California. Credit: Jeff Vespa/VF12/WireImage

Jennifer Lopez isn't the only one getting pampered by Casper Smart.

The backup dancer-turned-choreographer makes it a point to spoil her 4-year-old twins (with ex Marc Anthony), and stopped by a recent Xbox 360 event in L.A. to score some games for Max and Emme.

"He was going on about how he loves playing with them," says a witness.

Smart, 25, is equally enamored of his girl, 43.

"He's madly in love with her," the insider says of Smart, who will join Lopez on the European leg of her tour in October.

Adds the source, "It's not just that she's his lover, she's also his best friend."

Smart and Lopez first stepped out together in Fall 2011, just a few months after her painful July split from Anthony, whom she wed in 2004.

During her September 14 appearance on Katie Couric's talk show, Lopez opened up about the much-discussed 18-year age difference between her and her new man.

"Until somebody brings it up, I don't think we really think about it," the singer revealed. "We're just two people who have similar interests and love a lot of the same things and who get along."