His father MINAMOTO no Yoritomo tried to make his daughter an empress of Emperor Gotoba (at that time) to reinforce the government by making use of the Imperial Court, and Sanetomo may have succeeded in his approach to the Retired Emperor.
父である源頼朝は自分の娘を後鳥羽天皇（当時）の妃にしようとするなど幕府を固めるために朝廷の利用を考えていた面があり、上皇との接近はその継承とも解釈できる。