JENNIFER ANISTON may have finally found the man of her dreams — with one slight problem – his girl­friend!

The “Friends” beauty, 42, has fallen hard for her “Wanderlust” co-star  actor and screen­writer Justin Theroux, 39,  whom she met on the set of the film last year.

But NOW she’s finding herself in the middle of a love triangle! He’s been dating Hollywood stylist Heidi Bivens, 35, for years, say sources.

Heidi’s mom, Marilyn Bivens, re­cently told a reporter that Heidi and Justin – who wrote the script for “Iron Man 2” – are still very much a couple.

And she says that Justin has insisted that rumors of an affair with Jen are just a “big, big misunderstanding.”

But an insider revealed that Jen and Justin, who were “friends only” until recently, have now taken things “a step further.”

The two were spotted getting cozy at the Hollywood’s Sunset Tower Hotel.

Days later, they reportedly spent the weekend together at Jen’s Beverly Hills mansion and Jen recently threw a party at her home so she could introduce Justin to pals.

“They tried to keep everything top se­cret, but now Jen has stopped hiding him,” added the in­sider.

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