It annoys me to no end.

My wife's cousin is like a younger sister to us. We met her when she was 15, she's 28 now. We've been together since she was 21. My wife's cousin is 2 years oldest than me, and I'm 2 years older than wife. We call it the 2-2-2 rule. We're all adults. Her and my wife are like sisters, her and I are like brother and sister, but I fell in love with her. I've loved her since we met. I remember I was 17, her 15. She came to visit us, and we went to a bar, she had a fake ID. She was so intriguing. I loved her immediately. I never told her how I felt, but now, I don't love her, I'm just annoyed. I married her cousin. I haven't loved her for years. I used to daydream of us together, but now I think my wife is much more beautiful. The thing is, my wife doesn't care if my cousin and I bang, that's what she calls it. If I wanted to, I could. But I'm annoyed. Why can't I? Why can't I love my wife's cousin? Why can't I have sex with her? What law of society even says that? I don't love her anymore, even if I did, why can't I be with her? She's not related to me. She's my wife's cousin. She'll always be like a sister to me no matter what. And yet, I'm not allowed to be with her. I'm not allowed to have sex with her. I love my wife so much, and I don't want to betray her, but I'm just annoyed we live in a society that says we can't be together.