Wouldn't the most basic version of this be the pool of characters one could recruit to their court? A handful of people live in each county, get married, have kids, and can be brought into the local ruler's court for a small fee? If not doing anything, they retire into the local recruit-able pool. These characters don't do anything except have annual death, birth, marriage, and stat update checks. More features could be added later, but at its core this would be what the player would see when interacting with them.
As was said earlier, they'd also be used as local leaders for various things like revolts.
As was said earlier, they'd also be used as local leaders for various things like revolts.