I have a married sim (girl) who is also in a "budding romance" with a different sim.
One Sim can ask another to go Downtown, either in person or over the telephone.
There is no timer or scoring, but if things go badly, the date may autonomously decide to leave.
Otherwise, when the controllable Sim says goodbye, the date will end, and a pop-up message will appear, and will give the player a general idea of how the date went.
An almost elder father and teenage son should not be able to pass as twin brothers.
What happens if a sim has multiple romantic relationships with two or more other sims?