Need advice plsssss....anyone?

So I’ve been friends with these 2 girls since I was 5 years old. We all used to hangout but a few years ago they both had a falling out while I was away at college. To this day I still don’t know exactly what happened but they just stopped talking to each other. I don’t ask what happened because i don’t talk about them to each other o behind their backs if that makes sense.

So they haven’t spoken in forever. But I’m still really good friends with both of them and love them both. I have been hanging out with both of them without either of them knowing for a while now but I’m just ready to tell them that I hangout with the other.

I’m really hoping they don’t get mad when they find out. Do you think I should tell them? Do you think it’s wrong for them to be upset? It did happen a while ago so they may be over it. We don’t talk about the other girl because I’m friends with both and that would put me in an uncomfortable situation.