My big sister's finace?

She's getting married soon, to a guy named Jerk. Speaks for itself. He's a kiss up, and is kinda mean to my sister, but she still loves him. I don't know what she's doing! I don't even think he likes her! She's really pretty, I have to admit, so sometimes, I think that that's why he "likes" her. He also treats me like a ten year old. Yesterday was my 15th birthday, and he got me the Narnia series. I don't like those books. They're boring. Should I tell my sister not to marry him? Do you think he loves her? Is she making a mistake?