<human>: Can you condense the text into three sentences or less?

To make a long story short: My mom and I got into a huge discussion about infidelity and somehow my uncle was brought up. I did not know he cheated on my aunt, who is such a nice woman. My mom said that she doesn't condone my uncle's behavior but her loyalties lie with him because that's her brother and that I can't tell anyone. I got mad and asked her how she could look at my aunt for all of those years knowing that he cheated on her. She divorced her first husband because of infidelity so I'm sure that she doesn't know. I don't know all of the details and I don't really want to. She said she shouldn't have told me/compromised my relationship with my uncle. 

Infidelity is such a huge betrayal and it makes me sick to my stomach that my sweet, wonderful aunt was cheated on and has spent years thinking that everything was okay. My mom said not to judge a marriage and that theirs isn't perfect, but has conceded that they are not abusive toward each other or anything of that nature. In the heat of the moment I asked my mom how she could live with this information and she countered with: well how are you going to live with this now? Are you going to tell her? Now I feel like I'm in such a hard spot because I would ruin my relationship with my mom, my aunt, uncle and likely my cousins. Also I don't have any information other than what my mom told me -- I don't know who with, when (other than years ago) or anything of that sort, and my mom will not tell me. This is just a shitty situation and I really don't know how to handle this information. All I can think is that if I was married and cheated on, I would want to know. Ugh.
<bot>: My mom told me that my uncle (her brother) cheated on my aunt years ago. Aunt doesn't know. I don't know how to live with this information. I feel so guilty.