Anyone can call a boy son, but technically, your son has to be your male child. If you're male, you are your parents' son. Well done, son!
You can use the noun son for non-human animals too: "Our cat had six kittens, five daughters and one son." But it's far more likely that you'll describe human offspring as sons or daughters. Family names (or surnames) in many cultures include son or son of, like "Jefferson" or "Wilson," originally "son of Jeffrey" and "son of William."