Your son is 12 and half years old his penis is just 1.5 inches long what should you do?

Take him to a doctor to get hormones or have him start a daily penis enlargement routine. Although I'm not sure the 1.5 inches is erect of flaccid, if that is the erect length then I'd go the route of seeing a doctor and/or penis enlargement exercises, if that is his flaccid length he could very well be average (for his age) when erect. The average erect length according to an online source for a boy who is your son's age is about 3 inches give or take so 1.5 flaccid is not that bad.