I just saved one sim from Grim after she collapsed from freezing. She was on the street in front of my sim's house and my sim convinced her to group up. It would take too long to walk back to my sim...
I'm having the same issue. I'm losing like 3 sims per sim day, it's ridiculous. I populated my entire save with sims I made myself so I'm super upset about it. My population has been halved so far :(