Does my husband still love his ex wife?

My husband and his ex wife divorced because she was cheating with his childhood best friend. His best friend apologized and tried to save the friendship but my husband didn't want anything to do with him. My husband saw him on his people you may know on Facebook and clicked on his profile and his ex best friend is with his ex wife and they're expecting a baby. My husband looked extremely upset by this. I asked why he was upset. I'm his wife now. He said it's just the principal since his best friend was all sorry and stuff just to marry her. I got upset and asked was he still in love with her. He said no. I asked then why does he care. It shouldn't bother him. He said he can't help how he feels. His best friend is why his marriage ended and he told me a year ago his best friend reached out wanting to rekindle the relationship. So for him to a year ago try to be friends again and claim it was a big mistake just to now be married to her and having a baby with her he can't lie and said he's sour as hell. I just don't understand. They've been split up 5 yrs. My mom thinks it may also have to do with us not being able to conceive because of his fertility issues. We are currently looking into adopting but she thinks with us not being able to get pregnant but his best friend gets his ex wife pregnant it probably is triggering. Idk... Am I overreacting? Should he really be upset over this?