A Sim suddenly lost his relationships.

I've been using MCCC to get the new born-in game Sims to have a relationship with their relatives (grandparents, aunt/uncles/cousins), any time they come for a visit. It's vexing to have to constantly fix it when suddenly, the very next time they visit the Toddler/Child has to introduce themselves. My Sim family has only moved twice, but this problem cropped up with the latest patch. Seems things get fixed for a time, only to have another patch break them again. Oi! Glad I'm not a dev. That would give me such a headache.