We had families, so I think I can talk intelligently about this topic even though I am not in a sorority (yet! *crosses fingers*)
A lot of emphasis is placed on which family you join at my college. There were some that could trace their roots back to the 50's and some even earlier. All of our families were named after animals. One of my close friends was a member of the oldest family on campus, aptly named the dinosaurs.
I started my own family, so I am the grand matriarch of the parrots. I started with two little sisters, who each had two little sisters. We were pretty small and new, but now we are one of the larger families on campus, which is really amazing to me. I even have my roommate's biological little sister in my family now, which is neat. I gave her all sorts of parrot junk I had collected.
We also have family "friends" of sorts (certain families always hang out together and do special events together). In my circle of friends, we had three different families represented (dinosaurs, koalas and parrots). We all knew each other and genuinely liked each other, which some of the other groups didn't understand.
I'm actually glad I just typed all this, even if it's boring. It reminded me to send my traditions manual over to my baby parrots.