In January 1278, Yasumori acted as the bringer of eboshi at the coming-of-age celebration of Sadatoki HOJO, Tokimune's heir, and became his guardian.
建治3年（1277年）12月、時宗の嫡子北条貞時の元服に際し、泰盛は烏帽子を持参する役を務めてその後見となる。