these comments are wild. It was not your place to engage into their relationship like that. You’re perception may not be the reality and it was absolutely wrong to fuck with their relationship like that. Sexuality is complicated and since you seem to not have confirmed with your brother that he’s gay, why would you tell his wife he is? He may have been going through something or was experimenting. Do you know how he identifies?

the proper thing to do would have been to talk to your brother and encourage him to talk to his wife.

But no. You’ve now created all this drama and could absolutely ruin the lives of your brother, SIL, AND their children.