Jennifer Lopez spends Thanksgiving with her new dancer boyfriend Casper Smart in Hawaii, and children Max and Emme (pictured), Nov. 26, 2011

*Marc Anthony is reportedly incensed that his twins with Jennifer Lopez have been hanging around her new 24-year-old boyfriend Casper Smart, and according to Us Weekly, he’s determined to do something about it.

The Latin singer, who split with Lopez in July after seven years of marriage, reportedly “hit the roof” after he saw photos of the background dancer frolicking on the beach with Lopez and his 3-year-old twins, Emme and Max, during a Thanksgiving vacation in Hawaii, a source told Us Weekly.

“It caused a huge blowup,” the source said.

In retaliation, Anthony, 43, may go “back on his word” over the couple’s initial child-custody arrangements, opting to seek joint custody instead of allowing Lopez, 42, to take primary custody of the twins.

“He wants to make Jennifer suffer because she’s having fun with someone new, and he knows this will hurt her on the deepest level,” the source said of Anthony’s intentions.

But Lopez doesn’t plan to be a passive bystander in the pending legal fight.

The singer is “ready to smash him if he tries anything. … It’s getting vicious,” another source said.

Lopez and Smart were most recently spotted out and about in Las Vegas sharing a meal with fellow “American Idol” colleagues Steven Tyler, Ryan Seacrest and Randy Jackson Monday.