^It can be creepy. From my observations as an undergrad (and now as an administrator), it appears that some fraternities offer "lil sis" status to primarily freshman women who really don't know the purpose of greek life yet (or else they probably would have joined a sorority).
When I was an undergrad, one fraternity that had many Latino members (but was not a LGLO) tried to get freshmen women to join their "lil sis" program by telling them that it was REQUIRED if they wanted to have a chance at joining MY sorority!

