He was to be killed as the heir of an enemy warlord, but then allowed to survive because his mother came to remarry KIYOHARA no Takesada, the first son of warlord KIYOHARA no Takenori who had destroyed the Abe clan, and Kiyohira, as her child, was also adopted by KIYOHARA no Takesada.
敵将の嫡男であったので本来は処刑される運命にあったが、母が安倍氏を滅ぼした敵将である清原武則の長男清原武貞に再嫁することになって危うく難をのがれ、連れ子の清衡も清原武貞の養子となった。