OP, there should be a way in the relationship panel (Maxis should add one) to tag a Sim as a family member even after they grow up. I agree the game needs more ways to expand the family tree and include and be inclusive to extended family whether that is step kids and or in laws etc. If people don't want such a toggle as default then make it optional so the player can be inclusive to extended family members after they become adults. That would work for most people, I hope. Someone should ask again for a better family tree and extended to other family members even if adult, later. Or even yet, a popup to request if the step father wants to adopt the child before birthday or something since they are considered family until they age up. And it is not true the player controls TS4. No, a flirty Sim will flirt with anyone, a step child or not. So, no players don't have control over a situation that the game may invoke after the child grows into an adult. The game can cause the one Sim to flirt with this child/adult without any player input. So, no it's not something that can always be avoided or controlled.
