Adelphogamy (from the Greek adelphos - brother), or "fraternal polyandry", is a form of marriage in which two or more brothers share one wife or more.
It is found especially in certain areas of Tibet and Nepal, where polyandry is accepted as a social practice.
An example of adelphogamy can be found in the Mahabharata, where Draupadi is the wife of the five Pandavas.