Speaking of IVF, if a man has a son who is conceived after the father is already dead, is the son a yoresh? What if the brother did kidushin with the yerusha, is he not married?
Better, does the son conceived after he is already dead pattur his wife from yibbum? Or mechayev his sister in law in yibbum? How long does a widow with no kids or brothers in law have to wait to know that a brother will never be born? What if there is one live brother but she is an ervah to him but there is a tzara so according to beis shammai she is chayav in yibbum and she does chalitza, so now it is a safeik d’oraisah if the they are pattur even if there is another brother, so is it a sfeik sfeika now?
See, isn’t this more interesting than fighting over whether we should believe in daas torah?