jlocaspersidebyside460WM.jpgCasper Smart photo courtesy of leviwalker.com

Jennifer Lopez and new boytoy Casper Smart are getting hot and heavy in Hawaii, according to Us Weekly.

The mag claims the dating duo spent the Thanksgiving holiday together on the island of Kauai. Also along for the tropical trip ... JLo's 3-year-old twins, Max and Emme.

A source tells Us:

    "Casper was great with the kids. He was twirling them around and doing flips with Emme and she seemed very comfortable with him. Jennifer got a chance to sit back and relax while Casper took over and played."

Wonder what JLo's soon-to-be ex Marc Anthony thinks of this? Guess the "I'm Into You" singer is now officially into someone else.