Ok, so I started to take a whack at this (I'm a glutton for punishment).
Just to ensure I am following the rules correctly, the founding household can have more than 1 person in them, as long as it's not a generational household, and no one is a banned occult. And also, the heir must be the oldest child in the household, not just oldest of the founders (so if a housemate has a child elsewhere older than the heir, that child cannot be moved in).
Specifically, I'm looking to start with Connor Frio, but I can never move in Jared's child with Claire, even though Claire and Jared are not the heir's parents. However, I could ideally move a later heir in with Claire or the baby because Story Progression does weird things.