For me, it's the ugly kids, 😂! Like I'll have some really cute little sims and then suddenly all the next gen kids I can't seem to get attached to. I need to just stick it out and I'd probably get attached after a while.
(I edited out some comments about what ugly was in my eyes, but truly I didn't like myself when I said those things because everyone is beautiful. I think sometimes when we get bullied by a kid in junior high or find out someone betrayed us at our old church, people that remind us of them become what we think of as ugly. Anyway, I was just realizing why I might have thought some sims were "ugly".)