Yeah I also agree this Sims 3-esque feature would be a strategic one to add. But this would require an entire game overhaul because it would require aging of your toon and his NPC family.
The Dovahkin could have 1-2 children born to him in game. Each time you leave the home and return, time advances by a set timescale. (e.g. 8 hrs fast travel = 1 year skyrim time etc).
Then the challenge would be raising these kids (while adventuring/dungeon crawling/etc) and trying to keep them safe as heirs until at least their teenage years.
At least 1 child needs to survive into their teens, so you pick the heir of your choice to replace the Dovahkin/Tamriel hero in the event he dies in the game (which is frequent without the use of cheats and tgm)

But if the Dovahkin dies before any of his/her children become teenagers, then you'd have to begin a new savegame. So this DID style meets the Sims 3 would add some intresting challenge and strategy to the game.
There also could be an option to have the heirs accompany the Dovahkin as followers (both as children and older) so they can get XP fighting monsters/enemies, or just hanging out (fishing, hunting etc.) with Dad/Mom
But as Akul mentioned, this may not be possible for TES V due to potential synchronization issues with the game clock.

I do have hope for TES VI however
