I'm (20m) really in love with my (20f) little sister?

I'm gonna be 100% honest. I'm 20 years old and i am deeply in love with my 20 year old little sister. We are literally inseparable. We do EVERYTHING together which I know is weird considering we are both 20 so we should be doing different things with friends. I mean we still hang out with our own friends etc. I feel so bad about the way I feel. She is my best friend. I don't know if it's the fact that we are Irish and just don't talk about this at all. I feel really fucking weird. We both get really really drunk and have never done anything inappropriate. My biggest fear is when she finds a boyfriend, gets married, have kids etc and I will never see her the way I see her now. I'm so confused on how to feel about it all. It's not a sexual thing at all. I just don't want to be away from her.