Seiwa Genji
They are descended directly from Emperor Uda (868-897) by his grandson Minamoto no Masazane (920-993) (Uda Genji), but were adopted by the Seiwa Genji. Minamoto no Nariyori, great-grandson of Masazane, is the first who took the name of Sasaki from his domain in Ōmi province (now Shiga).