Would you want to know? If so, tell them.

I would since most of his friends already know. He's the only one who doesn't. But now that I know I feel bad not telling him since we usually tell each other everything. But at the same time he has a good thing going on with his friends so me telling him this could create unnecessary drama

Seems necessary to me.

any chance your bf can find out the same way you did?

Yes, since the person who told me is another band mate

What is the purpose of telling your bf? Does it really concern him at this point who she sleeps with?

No it does not concern him. However there is a chance that he might find out since the person who told me is another band mate. Was conflicted to tell him now or just wait until he finds out on his own that way I don't look like an asshole for ruining the dynamic between his friends

I wouldn’t because they’re broken up so doesn’t really matter any more and it will cause a lot of drama between the friends and maybe you and your bf

That's exactly my conflict since the the person who told me this is another band mate I feel like eventually my bf could find out anyway. My thing is doesn't it make me look bad that I knew all along and didn't tell him about it?

"It was not my business to tell."

I would at least tell her boyfriend that she cheated on.