Amago clan
He was born to Amago Masahisa in 1553. In the following year, Katsuhisa's father and grandfather were killed by Amago Haruhisa, leading Katsuhisa to become a Buddhist monk. After the Amago clan was overthrown by Mōri Motonari in 1566, Yamanaka Yukimori supported Katsuhisa against the Mōri clan in 1569. He lost to Mōri Terumoto at Nunobeyama in 1570 and fled to the island of Oki.