Weasleys. Granted, Harry's family all showed up round the same time. I was here first though, I think. And probably the longest. I dunno, hard to tell. Didn't mean nothing bad by that, mate.
I don't know who this would be harder for. I'm pretty sure if a daughter or son of my bout my age or older showed up, I'd freak. But no one past my timeline has ever showed up, so I think I'm safe.