It is said that his father Tsunemoto was one of the Sukemasa's senior vassals, and as he died in the Battle of Minoura as a scapegoat for Sukemasa, Sukemasa, with his gratitude, gave his son Tsunechika an important position.
父経元は亮政の重臣であったが亮政の身代わりとして箕浦合戦で戦死し、それに感謝した亮政は経親を重用したと伝わる。