Sims keep “forgetting” their extended family members!

i play on pc. i do not use any mods or cc in my game. 

i’m playing rotational gameplay with 4 households, but every time I switch between households, the sims are forgetting about their extended family in the other 3 households. for example, Katrina Caliente lives with her husband and their 3 children, her daughters Nina and Dina live in other households with their own families. Katrina, although having met her son-in-laws, doesn’t have any relationship to them. i’ll get them together and do a “friendly introduction”, but the next time i switch households, they don’t have any relationship meaning they don’t appear on each other's relationship panel whatsoever, even as an acquaintances.

do you have any advice or fixes to this?

thanks!