Draco Maloy is a vela, like his father. And, like his father, he has a mate. This mate appeared in Draco's crib when he was just an infant. Because of this, the Malfoy family had no idea who this child was so just kept him there and raised him. They kept an eye out for any missing posters in the Daily Prophet and one showed up. The baby and Draco had a special connection, you could feel the magic that surrounded them when they were together. To figure out what this was, the baby was taken to Gringotts and they found out he is actually Draco's mate. So the malfoys got custody of the baby and raised him with Draco.