To Yoritomo, the wife of Yoshiyasu was the only sibling still living and born to the same mother (MINAMOTO no Mareyoshi, Yoritomo's younger brother born to the same mother, died young in a war, and MINAMOTO no Yoshitsune was his younger brother but born to a different mother).
頼朝にとっては、存命の同母の兄弟姉妹は能保の妻だけだったのである（同母弟の源希義は早い段階で戦死、源義経などは異母弟に過ぎない）。