I'm planning to have a campaign with a lot of downtime. So much downtime, that eventually the characters get old and need to pass the torch to the next generation. Ideally, characters marry into influential families and raise children that can grow their estate. Alternatively, a character could adopt an orphan, and train them in the ways of their class to continue the 'mission'. Parents would try to arrange lucrative marriages for their heirs, and other such machinations.
First, I would need to normalize the lifespans of the different races, as having elves live so much longer than others would wreck things.
I'm interested in ideas that would encourage the characters to have an heir or two to carry on for them. Increased starting wealth from inheritance would be one. Along with inherited social status. I need a 'carrot' to get the players to be motivated to participate with their characters in such an endeavor.
If things go well, the story could continue with a third generation.
I can't seem to find advice or rules that would support such a campaign, beyond the basic down time rules which don't get into heirs and such.