Mine was back in Sims 3. I had a family of 4 that I was playing. The wife was my own creation, who was married to Vladimir Schlick (Bridgeport), and they had two children, a teen daughter, and a son who was still a child. I had become very attached to this family when EA had released a patch that was to fix a serious issue that was affecting all players negatively. But for the patch to take place we had to save our families to the bin, and then start a new game save, and then place our families in the new game save.
But when I tried to save my family, it would just not save. After some trial and error, I finally figured out it was the wife/mother who was causing the issue. I didn't have the heart not to save her husband without her, so I aged up the teen to a young adult and saved her and her brother. I ended up moving the sibling pair to Moonlight Falls. It was not an easy transition after the move either, because the sims of that town were always causing problems for the orphans. But eventually, things did smooth out for them, and their families did eventually progress and grow.