Princess Heather - I hope all your sisters realize how lucky they are to have you around! You sound like a gem!
My dad and mom never gave me any grief about my "sororitygirlitis". They were and are really cool about living their lives and letting me live mine so they pretty much always kept out of my business.
I always invited them to the Mother/Daughter Teas and Father/Daughter Brunches, though and they enjoyed going to those. My dad even used to sit with us at some of the football games until I put a stop to it because some of my sisters tried to hit on him. I mean, I know he's a nice looking man but he's my DAD for Heaven's sake! Sick!