Masamichi is the grandson of SAKANOUE no Tamuramaro (a military commander of the early Heian period), and the son of SAKANOUE no Kiyono according to 'Genealogical Chart of the Sakanoue Clan,' but is written as the son of SAKANOUE no Hirono in 'Montoku Jitsuroku' (fifth of the six official national history books).
坂上田村麻呂の孫であり、「坂上氏系図」は坂上浄野の子と、「文徳実録」は坂上広野の子と伝えている。