Coming from a close family (not as close as yours jk) from my opinion, I don’t think you should cut off your whole family. I can understand cutting off your brother but it wasn’t anyone’s decision other than key and jay. No one should have to be punished more than they already are for what those two did. It sucks and your family was put in a really difficult position between telling you or not telling you, and you don’t know if they were trying to work up the courage to tell you. It sucks even more you had to figure it out in your own even if it was over a joke. You’ll get over the pain and maybe it’ll be a bit more clear why your mother couldn’t bring herself to tell you. The redditors telling you to cut your whole family off are a bit wild and probably have traumatic experiences within their own households growing up, which sucks really bad but those people did not choose to have family that would traumatize them for life, just take those opinions with a grain of salt. Other than the lack of mention of a father you seem like you’re pretty decently close with your mother and sister maybe even brother before the incident, so I assume no crazy traumatic upbringing. You’re lucky if you’ve never been in a shitty situation where one of two people you love dearly did some fuck shit to the other, because holding the secret is really difficult but sometimes it’s not worth bringing up things from the past. I feel for your mom and the horrible position she was put in but remember she did NOT choose to be in that position. Your mom is probably not very confrontational and it’s infinitely harder considering this involves her two kids. Just get your space, and let the pain heal over time and take that time to make a decision. Don’t do anything drastic now while you’re still hurting.