AITAH for getting pregnant by my brother in law?

My husband (M32) and I (F37) kinda got set up by our parents. His father and my father were always very close and my father was like a mentor to his. We’ve been married for 10 years now and when we first started dated everything was perfect. He was very sweet and romantic and we decided to wait until marriage to have sex.

The night of our wedding was the first time we were very intimate. That night I conceived our twins, and ever since then my husband and I never were intimate again. He was cold and distant seemingly overnight. He wouldn’t hug me or kiss me despite my pleads and my constant bringing it up. My entire pregnancy was lonely and I cried constantly because of this. It was at this time I realized my husband has also been having an affair. I still don’t know who it is. But he would be gone all night claiming he’s at work, and be on the phone constantly.

After having the twins I began to confide in my husbands brother (M25). My brother in law has always been very kind to me despite kind of his being the black sheep in his family. I’ve always found him somewhat good looking but I never thought much of it. One day while I was confiding in him he confessed his attraction to me and we began an affair. I found out I was pregnant in my second trimester and had to tell my husband. He barely reacted though!

He has to know it isn’t his because we haven’t been intimate in years, but he was very calm and said we would raise the child like we did the twins. And I don’t know how to take this. He should atleast want to know who the father is right? My brother in law knows he’s the father and I just don’t know how to feel. I guess since we both have been having an affair it’s fine? But I feel completely uneasy. Am I the asshole? And is it wrong to have my husband raise his brothers child without telling him whose the father?