Jennifer Aniston's "guarded" relationship with Hollywood funnyman Vince Vaughn is the result of her parent's divorce - not BRAD PITT - a friend of the star insists. THE BREAK-UP co-stars have infuriated the press and fans while promoting the movie this month (JUN06) by refusing to confirm their dating status, and Aniston has proved particularly wary of discussing her feelings for Vaughn in interviews. However, close pal JIM CRUSE insists her reluctance to show affection isn't the result of her traumatic split from ex-husband Pitt last year (05), but her troubled childhood with her father. He says, "She is guarded with her emotions. I think her hesitation to commit comes from having had a father who left home when she was a very young girl, when he divorced her mother. "On some level, I think it's made her believe that men are prone to leave her, and she wants to leave them before they do it to her. I really believe that. "I have a sense that Brad didn't feel she was totally committed to him. Let's put it this way: when that marriage ended, people in the inner circle were not as surprised as you might think."