I play with a lot of long lived/immortal Sims, hence, people who can have adult kids and still appear to be young adults themselves, but CAS won't allow a child to be in the same age group as the parent. This makes it difficult for me to make multi generational families. Does a mod that gets rid of this exist? I get the feeling that it doesn't because it's probably a pretty niche issue, but if you happen to know anything about it I appreciate it!

Make these sims like a casual roommates, then in-game use MCCC to set both of them as parents of the rest.

Thank you for the tip!