Then red flag:
I actually spoke with his mother recently. She first asked if I was really happy with him and then told me that her son has always been an odd child. He used to be mean to his classmates (sometimes going beyond the ''kids can be cruel'' limit). He got expelled from school once. His previous relationships didn't last more than 4 months; sometimes it would be over within weeks. She claimed her child isn't really the sweet angel he acts like. Her voice sounded of concern.