This is a quotation from Genesis, and refers to the story of Isaac and Rebecca, and their two sons, Esau and Jacob. Esau and Jacob are twins, and when Rebecca is pregnant with them, it is prophesied that the "older shall serve the younger." This was completely against the customs of that time and place, in which the older child inherited everything from the father, and in the case of Judaism, received the father's blessing. One twin, of course, being born first, is considered the elder twin, and in this case, Esau was born first, but Jacob manipulates events and deceives his father into thinking he is Esau. In this way, he receives the inheritance and his father's blessing, thus making Esau the brother who must "serve" him. The story goes on to tell us that Esau marries outside the Jewish faith, and in fact, one of his wives is the granddaughter of Hagar, Sarah's handmaiden in the story of Abraham and Sarah. You might have learned at some point that Hagar and Abraham cohabit when it appears Sarah is too old to have children, and Hagar and Abraham's child is Ishmael, who is said to be the beginning of the Arab nations. To get back to Jacob from that little detour, Jacob remains in the faith and is responsible for the continuation of the tribes of Israel.
Whether or not you believe in the Bible literally, these are wonderful stories about human emotions and behavior, and they have much to teach us.