It is believed that Mitsumune, like his father, served as a trusted vassal of Imperial Prince Morihito (Emperor Nijo), and he and his father acted together when the Heiji War occurred in 1159.
光宗も父と同じく守仁親王（二条天皇）に近侍したと考えられ、平治元年（1159年）の平治の乱では父と行動を共にする。