should I tell my husband about what his father did 20 years ago

This is a throwaway account, but I am 20F and my husband is 24F. We have a four month old and are doing really well right now. We live with his family. His mom and dad have been divorced since my husband turned 18 but they still live together, sleep in same bedroom etc... Over the last 6 months of living here I have learned the real reason why they got divorced from my husbands mother, aunt, and grandmother. My husband thinks they got divorced because of money issues revolving his brother who is in and out of prison. I have learned that the real reason they got divorced is because my husbands father had been having an affair and even got this other woman pregnant. I am not sure if this woman got an abortion or if my husband has a secret sibling somewhere. My mother in law stayed married to his dad until my husband was 18 because she didn't want to "ruin his childhood". Well my father in law is a very rude person and is constantly degrading my mother in law, calling her names, not helping her out with money or things around the house ect.. my husband i think has a little bit of resentment towards his mother because he doesnt understand why she doesnt love his dad anymore. this results in my husband also being rude to my mother in law. I hate watching him idolize his dad when he does not know the full story. Everytime I look at my husband I just feel like I am hiding something from him. I can sit with the guilt my whole life if it is the wrong thing to tell him. I truly just cant tell what the right thing to do here is.