Although his father Iwatari had been alive until Toshitari became more then 40 years old, his first investiture was very late: it was finally taken place when he was 47 years old, and it was after Iwatari's death.
父石足は年足が40歳を越えるまで健在であったが、初叙はかなり遅く、石足の死後である、47歳の時だった。