Tough Riddle!

Today's riddle almost had me stumped! I ended up having to take out some scratch paper and sketching some complex family tree diagrams to figure it out! Thank goodness I was finally able to solve it, because I didn't see anyone else returning to the common room while I was out there... I don't know where everyone was, but I was getting nervous that I might end up sleeping curled up on the floor if I didn't figure it out soon! I wish it hadn't kept me from my homework for so long...now I have to catch up on that before I can continue knitting my newest sock project.