Ex and other relationships

My most recent ex-boyfriend and I have only chatted a few times since we broke up. He is very nice. I spent a good portion of our relationship hanging out with him and his friends and family. I did this mostly because I don't like my family and I don't really have any friends of my own. Recently one of his very close friends has been messaging me in a "hey how are you" way. Tonight I'm concerned that changed. When I was dating my ex the friend was dating another lady. Unfortunately their relationship didn't last. I felt like my ex's friend was kind of hitting on me tonight and I don't know how to feel about it. Any thoughts?