Affair

My dad cheated on my mom when she was about 6 months pregnant with me. She found out the next day (the other woman was a mutual friend), but didn't let him know that she knew until right after I was born. After the divorce, he and the other woman got married and moved to Florida, and I wasn't even 6 months old when that happened. Haven't heard from him since then.

My mom was able to find love again a few years later, with another woman. They got married last summer after it was made legal here in Wisconsin.

It will take time, but your mom will eventually recover, with the right support from the right people. Sorry, I'm kinda bad at giving advice. I'll shut up now.

It is hard to approach a topic like this and not totally feel empathy for the children involved. I was one of the fortunate few in today's world where my father and mother were married until the day my father passed. I completely understand the resentment that you feel and I guess I can attempt to make a comparison. I was shipped home to attend my father's funeral the day I was informed of his passing and in an extreme emotional fog. When I came home and saw my family, my mother seemed out of sorts and there was a strange man making himself comfortable in my father's home. In a short time after meeting this all too comfortable stranger, I drew the conclusion that he and my mother were having a go. Not even a few days after my father went to his little acre of Valhalla, this man was spending nights with my mother.

I viewed this as cheating because there wasn't an acceptable grieving time in my mind. I still cannot look at my mother the same. I have, in my way, attempted to forgive because I know I had said some truly harsh things the moment the conclusion dawned on me, but I don't think I will have the ability to fully forgive her for that mental lapse in loyalty.
My mother and I have talked often about that situation and she understands that a part of me felt that my world view was betrayed by her actions. She and I have discussed the conversations her and my father had before his passing, but still, when a child has their parents teach them loyalty and faithfulness only to have it blown up in your face, it is really hard to come to terms with.
On the flip side.
Your mother did her best to shelter you from the complexities of her relationship with her husband. Your dad was acting foolish, but obviously acted out. There is always a reason behind the choices we make. Were there unseen late night discussions? Had she already known? (You cannot fool a woman who has known you for 25 years.) What were the issues your parents were facing? Did she pour too much of her heart and soul into her children? Did he feel unwanted and burdened by the basic need for physical and emotional connection?
Look at it this way, can you truly state that if you were in your father's position right now, you would not make the same mistakes? If you can say that you wouldn't then I understand why you cannot forgive him and I give you kudos for the morality you live by. However, if you can honestly say that you don't know or that you may make the same mistakes, then be honest, can you forgive his flaws?
I am biased. I idolized my father. I am learning to forgive my mother, nearly ten years after the fact. It's really hard and I get it. Just be there for your mom and in time ask her or your dad what the reasons were for his repeated indiscretions.
Good luck and I am really sorry you had to go through that. Thank you for taking the time to reach out and ask for advice.

This is really hard for me to relate to and I don't have any good advice to give you. For that I am sorry that I could not be of any help.

However, many other users have given you great advice and you should listen the them as I think it will be helpful to you.

I wish you the best of luck in working through this situation.