The couple secretly separated a month ago, almost 18 months after getting engaged.
Insiders claim one of the factors behind their split was the Snow Patrol rocker's unease at the fact the 'Cougar Town' actress, who previously dated her co-star on the show, Brian Van Holt, and met ex-husband David Arquette on the set of "Scream", is very "close" to the men she has worked with, reported the New York Post.
"He's actually the one who instigated the breakup. Johnny feels she's a little too close for comfort with her male co-stars.
Cox, 51, has been left devastated by the split.
"Courteney is super upset about it. She wants to be with him. She's told everybody that this is the most she's ever been in love with anybody, more than with David or any of her exes.