Before the twins' birth, Numitor had been usurped by his brother, Amulius. After seizing the throne, Amulius murdered Numitor's son, and condemned Rhea to perpetual virginity by consecrating her a Vestal. Rhea, however, became pregnant, said to be by the god Mars. Amulius had her imprisoned and, upon the twins' birth, ordered that they be thrown to their death into the rain-swollen Tiber. Instead of carrying out the king's orders, his servants left the twins along the riverbank at the foot of Palatine Hill.