There's more to the split!

X17online has learned exclusively that in addition to her issues with the actor's pot smoking and parenting style, Angie was insanely jealous of his close relationship with Allied co-star Marion Cotillard. AND guess what -- Marion is pregnant! The French actress just confirmed in a cover story for Closer magazine that she's with child, though no one seemed to be speculating when the French actress showed up in a voluminous dress on the red carpet at the Toronto Film Festival last week. And funny enough, Marion didn't talk about her plump belly -- she let her Juste la Fin du Monde pregnant costar Lea Seydoux take the spotlight.

So why didn't Cotillard want to talk about her baby news? Maybe because Brad Pitt's the DAD! The French actress, who won an Oscar for her role as Edith Piaf in La Vie en Rose, has been with long-time partner French actor/director Guillaume Canet since 2007 and they have a 5-year-old son Marcel together. Reports from Paris say Marion is due in December. That puts the date of conception in March, when she and Brad were filming Allied together in London. By April, news was leaking from the set that the two might have been carrying on an affair. Even the film's director, Graham King, said Cotillard and Pitt had an unusually strong chemistry: "Brad and Marion immediately had the utmost respect for each other, so once they delved into their characters, their chemistry was electric," he told People magazine.

And a source tells X17:
    "Angie couldn't handle Brad's sex scenes with Marion. Her jealousy was out of control. Brad tried for months to reassure her and calm her anxiety, but it simply didn't work. She said her intuition was telling her he was cheating."

Cotillard and Canet never tied the knot but they were seen together on September 10, with their son, in Bordeaux, France for an environmental gather -- Marion is a spokesperson for Greenpeace. Obviously Canet assumes he's the father of the child ... but is it possible he's not?!
    "Angie has struggled with insecurity over Brad's fidelity for years, but she was never as jealous over a co-star as she was with Marion. She was always paranoid Brad would do to her the same thing he did to Jen," the source tells us.

Would Brad actually shack up with Marion and raise their baby together, leaving their long-time lovers (and families) in the lurch?

Daniel Smith/Paramount