Has anyone accomplished the Legendary Legacy achievement?

Its just that the game "forgets" sims that, in my case, have been dead for a while and have no relationships with alive sims. Its happened to the aunt's and uncle's of my legacy sims, who never went on to have children themselves. However, I've never had the game cull a Sim who has living children, grandchildren etc... That's why I primarily stick to one pregnancy per couple.