Husband thinks sister is hot?

He never told me this, but i read from his txt message w his cousin that he agreed w him that shes hot.

Anyways, hes asked about her a lot. Like ask what she does in life and all, i have 3 older sister, and he never ask about them.

We once went to visit, we both bought food for them. She was there too, and he told her to eat. She refuses and said she needs to leave, but thanked us. After she left, he got upset at me for not forcing her to eat, or at least pack some for her.

Then, one time they both were talking, after she left, he wanted to have sex w me. And was all horny, making me think he was probably horny for her, and wanted to have sex.

Also, another when we both were over, and we argued. He made it a big scene, my sis who he thinks is hot, yelled at him. And he immediately stop saying a word. But went back to yelling at me for a few mins passed. Then, she pulled him away to talk, and he talked to her about our problem.

Idk, i just have a feeling hes really into her. And it makes me damn uncomfortable, whenever we have fam gatherings!! She is his ideal woman...

This just makes me want to leave him. What should i do?