It's hard to think about your significant other having a romantic life outside of the one you share with him or her, but there's no changing the fact that there were others who came before you. It's tough dealing with those who your love stays in touch with, but it may be even more difficult to deal with those who he'd rather not hear from again. We're talking about the so-called "crazy" ex. She's the one who calls him at odd hours, harasses him on social media and otherwise makes everyone wonder what he ever saw in her. It may be hard to look past her erratic behavior now, but at one point, he really did care about her. Perhaps they even made future plans to get married. It's important to be respectful of that history, though it should be behind him now. Ensure that he's completely over her before proceeding in your relationship.