My biggest family tree is massive. It'll take me days to provide pictures that cover all of it. I just counted roughly 80 sims without adding any of their partners. They are the two founding sims plus their descendants.
EDIT: Some time ago I had a go at making a thread about them just to try to keep track of their family tree.
https://forums.thesims.com/en_US/discussion/916663/patience#latest
Since I posted this info there have been several babies born to various members of the extended family.