I would tell HIM that you know .. But I would leave it up to him to the tell the ex wife is he chooses to. I imagine she will find out (as well as everyone will know eventually) when it becomes known that he has and is supporting another child.
My brother got another woman pregnant 7 months ago. Should I tell my brother I know and also tell his ex wife? His ex wife and I are very good friends. It's wrong, she's helped him turn his life around. They have a 5 y.o. kid.
Now youre about to tread where Angels fear to go. They are divorced so there really isn't anything illegal here so it sounds like you can't hold a secret and want to be big girl on Campus.
If its a matter of live and death, then by all means tell them otherwise keep it to yourself and move on, but there really isn't anything to be solved here by saying anything
Tell your brother that you know and ask him if his ex knows. If not let them work it out by themselves if you told her it would make things worse. If he doesn't come out and tell her tell your parents and ask if they can have a talk with him or even tell her. I hope everything works out :)
Jerry Springer show
No point of telling her cos they are not together any more. It will only be a hurtful memory for her
As others have pointed out, they're divorced. What does it matter that he's having a child with someone else? This is no juicy piece of gossip to be spread - this is not your news to share. Not your circus - not your monkeys. As Ann Landers was fond of saying - MYOB.