My earlier comments were based on the game's genetics, which is what I thought your original question was about. What people "see" as far as resemblance goes, is subjective. I base mine in the first instance to what I see but always confirm by comparing slider positions.
With mods you can add anyone to a family tree so I imagine the developers and creators had tools to do that without having to play a family for generations to fill graveyards with ancestors for the residents. I think it's interesting that people take the lore seriously. I have been told I lack imagination (which is fine by me) and only believe what I have learned about the game's genetics by raising hundreds, perhaps thousands, of sim babies over the years in many saves which span generations.