What Guys Said 1
If your age is actually 18-24 then I doubt he likes you. I don't mean this in any negative way, but the only guys I know to call a girl "sister" are gay. If you're younger though, then maybe. A guy who's just learning how to talk to girls will take any convenient excuse to strike up a witty convo.
What Girls Said 1
um . I don't know its probably like some kind of slang. on the other hand if it isnt, then maybe he does like you but as a friend. Usually when a guy calls you sister, its because they see you and love you and care for you as if you were thyere little sister, which if your crushing on this guy, is obviously bad. i hope this helps you!