He was born as the first Prince of the Emperor Monmu, but his father died when he was seven years old and his mother Miyako developed mental illness and thereafter she did not see the Prince for a long time (the Emperor was thirty-seven years old when the Emperor met Miyako who had recovered from mental illness after the Emperor began to understand things).
文武天皇の第一皇子として生まれたが7歳で父は死没、母の宮子も心的障害に陥りその後は長く皇子に会う事はなかった（物心がついた天皇が病気が平癒した宮子と対面したのは天皇が37歳のときのことであった）。