Most Helpful Guy
Three is two reasons:
1. Either he had realised his mistake and came for a true real second chance. But I will not based on that as today generation are messed up. It can happen but really low possibility.
2. He need a girl to have sex with, and a girlfriend is the a guarantee to get laid sex.
Bearing in mind you said exes, so it is second option which put a new question that you have to answered.
Why they are coming back to you and date you and have a relationship in order to get sex from you?