So about a year ago, I invited this guy to come to dinner with me, my friend (a girl), and another friend (a girl). I didn't know these girls or the guy very well, but we got along so I ate with them after practice. The guy hit it off with one of my friends and eventually they started dating.
During their relationship, I first became best friends with the guy — we talked on the phone every day and we got along better than anyone else I knew. He was the sweetest, funniest, most awesome guy that I'd ever known. His girlfriend would get jealous, which would make him question whether he should still be my friend or not. He ended up changing a lot after the first few months and I know the person that he is now is not the real him. All the fun times we shared just went away, but he's just acting like that to make sure he doesn't fight with his girlfriend — which they do anyways.
After he started changing, I ended up becoming friends with his girlfriend. Eventually, we became really close. But I never really approved of their relationship because they're bad for each other. She made him change because of me, and now that he's changed, he's making her even more sad in the relationship.
I feel like I'm the reason for their problems. They ask me for advice every time they get into a fight — about once a week — and I really, really want to tell them to just break up, but I'm afraid that I'll lose one of them in the process. I have no idea what I should do. Should I help them by telling them to get out of the relationship altogether? Or should I just let them keep doing what they're doing so that they figure it out on their own?