Jewish Tradition Speaks of Moshiach Ben David and Moshiach Ben Yosef

Jewish tradition speaks of Moshiach ben David and Moshiach ben Yosef. The term "Moshiach" unqualified always refers to Moshiach the descendant of David of the tribe of Judah. He is the actual final redeemer. Moshiach the descendant of Joseph of the tribe of Efraim (also referred to as Moshiach ben Efraim) will come first, before the final redeemer, and later will serve as his viceroy. The cooperation between Moshiach ben David and Moshiach ben Yosef signifies the total unity of Israel, removing the historical rivalries between the tribes of Judah and Joseph.

(From Mashiach by Rabbi J. I. Schochet)