Is it normal that i kinda want my sister to wear a skirt?

I mainly ask this because my sister is coming up to visit me at college somewhat soon. She isn't hot to me (although I think some friends think she is), she's just sorta plain in the face. Her butt is pretty great though. She also rarely ever wears skirts, although I know she has one since she wore it several months ago (I just assume she still owns it). Is it normal that I really really really want her to wear that or any skirt around me when she's spending time with me up here? Not only does her butt look great in it, skirts are just plum sexy...usually.