My husband has feelings for my sister

My husband confessed to me today that he has a crush/feelings for my younger sister.

For context, we got married last year with a grand wedding after a 6 year relationship. Our relationship has been great and he has been the most caring, loving person I ever had. We had our share of fights. When he confessed this to me, I asked him why do you like her now and what changed between us. He said he realised he & my sister have more common traits in them and he has basically fallen out of love due to me being prioritising work over relationship in the last 2 years. He caught feelings for her since start of last year but could not do anything since our marriage was fixed and parents had met. To make things more complicated, my sister has a boyfriend but it’s not a serious relationship.

I am stuck and confused now. What should I do? I love both of them.

If I divorce him, I would break him from my family forever. If I shut off contact with my sister, I lose my relationship with my family. There is no point now in me being any important in this relationship. He takes care of me but we have stopped being physical and he does not want kids if he is in love with someone else. Should I let him confess this to my sister?