Ephraim was the brother of Manasseh and the son of Joseph and Asenath, a woman whom was given to Joseph as a gift from the Pharaoh.
Jacob adopted the two sons as part of the tribe of Simeon and Reuben. Ephraim received the blessing of the firstborn, although Manasseh was the eldest, because Jacob foresaw that Ephraim's ancestors would be greater than his brother's (Genesis 48:13-20).
The tribe of Ephraim settled in central Israel, stretching from just west of the Jordan River to the central coast of the Mediterranean Sea.
Sources: Bridger, David. Ed. The New Jewish Encyclopedia, NY: Behrman House, 1976; Navigating the Bible II