I have a friend like this. She’s a girl tho, her boyfriend right now is her first bf but she was not the first gd of course. She actually told us about the past of the guy since the guy talk about it so openly to her and she just listen and she loves listening about the past of the guy. The thing is there are times that those past are hunting her too, she’s always thinking about what if’s in their relationship specially the kind of work the guy has- seaman. They are still together and I think it is because both of them are living in the now moment instead of focusing about the bad past of each other.