Be careful guys the stupid family tree bug, I noticed sims that may not seem to be connected to the family tree are still connected to the family tree. Sims that are not blood related, but marriage related to your sim you can do romantic interactions, but it will not register as such and does not count towards the serial Romantic trait of completion, some relationships are preserved if they came from the same household.
Edit: these sims will no longer get the option to Woohoo or mess around or get married to a related sim. If your sims family tree have lost the link to the parents because of curring the random unknown sim makes your sim related to everyone so than your sim will no longer have the option to woohoo with any sim.
Edit: Broken family trees are common with downloaded households, especially if the other sim also has a broken family tree.