"Chris is crazy about Jen but wants to be able to do what he wants," a source tells PEOPLE
“Chris doesn’t really want the relationship to end, but he needs to be flexible so he can see his family as much as possible with his own work schedule,” says a Martin source. “He’s crazy about Jen but wants to keep his own schedule and be able to do what he wants when he wants to do it.”
VIDEO: Jennifer Lawrence Poses Nude with a Snake
According to a Lawrence pal, the Hunger Games actress got “tired of Chris being so noncommittal.”
Both stars have also been busy with their own careers, which may have played a role in the split.
“Jennifer’s been pretty good about sharing Chris with his family, in part because she has been too busy herself to have it become a real problem, but she still wants to see more of him,” says the Martin source.
It also may not be the end of the road for Martin, 38, and Lawrence, 25, who partied over the weekend with her pals (and Kris Jenner!) at a belated birthday bash.
“They still care about each other, so I can’t say the romance is completely over,” says a source close to Lawrence.
•Reporting by LINDA MARX