Sims 2 frequently generates the same batch of dormies over and over, until you move some of them out or they die. Sometimes I find it kind of fun. "Oh yeah! You're that guy my mom told me about! Sure, lets go on a date." I even sometimes use the "no dormie regen" mod to keep the same batch of Sims on purpose. If you get really annoyed by them, just put a cowplant out in front of the dorm. Townies and Dormies love that thing and will quickly kill themselves.
I'm okay with them returning, I was just shocked both of them returned with a new sim I created.
