The former couple - who split in July after seven years of marriage - had agreed an amicable arrangement where the `American Idol` judge was primary carer of three-year-old Max and Emme, but the Latin singer is now said to be seeking joint custody.

Sources claim Marc "hit the roof" when he saw pictures of Jennifer`s new boyfriend Casper Smart bonding with the youngsters.

The insider added to the new issue of Us Weekly magazine: "It caused a huge blow-up.

"[Now he is] going back on his word and saying his wants joint custody."

Those close to the situation insist Marc`s motivation to take action is to make the `On the Floor` hitmaker "suffer" because he is angry she has found love again.

The source said: "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."

However, the singer-and-actress is not prepared to give in to her estranged spouse and is ready to fight him to keep the custody arrangements as they are.
sections: Celebrities