No households with children, period. It doesn't matter if the child is unrelated, or an adult living with their parents, or whatever. If you want to start with someone from a household with a child, start in an eligible household and have someone choose them as a co-founder.
No founding a dynasty with a teen and starting in their household. You can start in an eligible household and marry a teen when they come of age, but because aging up early is not allowed for this dynasty, not every teen will age up in the necessary amount of time (six days or less). So while Bebe Hart would be eligible for a founder to pursue because she ages up to young adult in three days, VJ Alvi is not because he's too young.