The originator of this clan is OE no Suemitsu, the fourth child of OE no Hiromoto, a reputable vassal of the Kamakura bakufu (Japanese feudal government headed by a shogun); therefore, they are the descendents of OE no Hiromoto, but not from the main branch of his family.
家系は鎌倉幕府の名臣大江広元の四男・大江季光を祖とする一族、したがって大江広元の子孫ではあるが嫡流ではない。