After the death of Sadamasa, his older brother, Tomomasa had Tomoyoshi, his own son, be the family head and he himself became the son's conservator, but had been losing power due to the advancement of Soun HOJO into the Sagami province.
兄定正の死後、自分の子である朝良を当主としてその後見役となったが、北条早雲（北条早雲）の相模進出に伴い勢力を失っていった。