Does he really want to be my "brother" or something different?

This guy who i like a little told me he wants to be my replacement brother for when my friend (who treats me like a little sister) goes to college. This guy always seems to want to touch me...making up handshakes, giving high fives, pushing my hat in front of my face etc. also he calls me by a name that only he calls me by, sort of like a pet name. so i kinda thought he was a little flirty with me although he's not really a very flirty person (unlike my current "brother") but when he said he wanted to be my brother next year i was really confused, you cant like your little sister that way so why would he like me? what does he mean? thanks for the help!