Jennifer Aniston’s sudden split with Justin Theroux was not so sudden after all!\n\nRadarOnline.com has exclusively learned the Friends actress’ relationship with ex Brad Pitt, 54, had a hand in the deterioration of her two-year marriage to Theroux, 46.\n\n“The one thing that Justin was always insecure about was her relationship with Brad,” a source close to Theroux said.\n\n“Jen and Brad never really stopped talking but after his split with Angelina, the two have been talking non-stop.”As previously reported, Aniston turned 49-years-old on Feb. 11 and spent the occasion without Theroux, who jetted off to NYC. Instead, she was surrounded by gal pal Courteney Cox, 53, among others.\n\nAccording to the source, “Her intense talks with Brad is what drove him to leave her this week. He ditched her on her birthday and went to his place in New York. She was basically forced to spend it with her friends.”“While celebrating with her friends, she was an emotional train wreck and she called him while she was with her friends still,” the insider told Radar.\n\n“But it was too late. Brad was the final straw for Justin. At this point, he really believes that her and Brad will get back together.”\n\nDo you think that Brad Pitt and Jennifer Aniston should get back together? Sound off in the comments below.\n\nWe pay for juicy info! Do you have a story for RadarOnline.com? Email us at email@example.com, or call us at 800-344-9598 any time, day or night.