Throwaway for obvious reasons. Hi Reddit, so… basically the title. I found out last weekend that my mom has done something… pretty inconceivable. I’m not really one for therapy, but I’m considering going just based on this new nugget I found out.

For context: my mom is a pretty severe alcoholic. She’s been fucked up most of my life. She’s got a lot of trauma (adopted, father was a wifebeater, coke addict when she got pregnant, pretty absent mother figure in general.) I love her, but have kept her at arm’s length for most of my life. My grandparents raised me and I couldn’t be more grateful. However, it was my maternal grandmother’s birthday last weekend and I hosted my mom and her husband at my house when they drove out to celebrate. I was anxious for how she would act, but overall the weekend went well in general - with the exception of Saturday night.

My grandfather and I had been planning this weekend for a few months. This was a milestone birthday for my grandmother, and she’s the matriarch of our family. We’re a small, not super close family, but he wanted to make it really special for my grandmother. So, he invited all three adult children (my mom and my two uncles) with their families to surprise her. When we were discussing the guest list, I asked about my youngest uncle and his family if they would be attending. He got very serious and said that my aunt refused to be around my mother, and that she would not be attending. I was obviously confused, and he asked if I knew what happened. I didn’t, but thought I could reasonably assume there had been some rift between them - genuinely thought that, as sad as it sounds, she had said something racist / out of pocket / overly mean, as she is wont to do. My aunt has always been a bit sensitive and a black sheep in the family from being the second wife, so I figured my mom had just done something fucked up in a state of alcohol fueled bullshittery. Sad, but nothing I wouldn’t put past her.

Cut to Saturday night. We had some drinks, we come home, my partner and her husband both toddle off to their respective beds and leave us to bond. After a couple of hours of talking through some other stuff, I casually asked what the issue was between her and Katherine (fake name, my aunt) - just looking for clarification / confirmation of my assumptions. She immediately shut down and looked really ashamed, and said she didn’t want to tell me because I would judge her. I told her she didn’t have to tell me, but I assumed it was as I initially thought. I did not press her again. About five minutes after my question, she comes out with that she slept with William (fake name, my uncle) after he and Katherine had gotten married. This would be anywhere from 12-15 years ago.

To say I was shocked is an understatement. While yes, they are step siblings - she was 14 when they met (him 9), and while they did not live together for most of their lives (he lived with other family from 9-12, and by the time he moved home she was pretty much out all the time)… they are siblings. We’ve spent multiple holidays together, I look up to my uncles as siblings I never had, etc. The idea that this happened is so incredibly sickening I don’t even know what to do.

Obviously, once becoming sober, this is not something she will discuss with me. I finally have something to put my finger on when the tension in the room feels awkward in a full family setting, but I don’t know what to do with it. I’m struggling on if I should tell my partner, who I’ve been dating for about 2 years and plan to marry, but doesn’t really get the complicated relationships in my family. Mostly, I just feel grossed out and confused, and burdened with this secret that doesn’t really have anything to do with me… on top of also feeling so, so awful for my aunt. She and I aren’t close, but I’m really struggling with the idea that she may view me differently just because of the kind of person that mother is. I’m also having a hard time viewing my mother in this new light.

So, Reddit… what do I do?