While difference in parenting choices has been cited as the reason for the divorce filed by Angelina Jolie and Brad Pitt, rumours are rife that the actual reason is something else.

According to reports, it was Brad’s proximity to ‘Allied’ co-star Marion Cotillard that caused the rift between them. Apparently, Angelina had hired a private eye to keep a watch on Brad as she felt he was fooling around and the detective confirmed the same.

Pitt, 52, had been rumored to have been cozying up to his “Allied’’ co-star Marion Cotillard, 40, for months during the pair’s filming of the World War II drama in London.

The PI discovered that Pitt was cheating on his wife of two years with Cotillard — while also partying like a single guy on a mission, the source said.

“The atmosphere [off-set] was full of hard drugs and Russian hookers, and Angie was told Brad got caught up in it,’’ the source said.

“He’s in the throes of some insane midlife crisis, and Angie is fed up.”

But a source close to Cotillard denied the Pitt affair rumors and insisted she is still with her long-term partner, French actor and director Guillaume Canet.

“They are still very much together. They have been a couple since 2007 and have one child but have never married,’’ the source said of Cotillard and Canet.

The source could not confirm French reports that Cotillard is pregnant with her second child with Canet