According to the inscription on the base of the principle object of worship in the main building of Myoho-in Temple's Rengeo-in (Sanjusangen-do), the first son of Kokei was born in 1173, and it is therefore estimated that Unkei was born sometime in the middle of the 12th century.
長男湛慶が承安3年（1173年）生まれであることが、京都市・妙法院蓮華王院本堂（三十三間堂）本尊の台座銘から知られ、運慶は12世紀半ば頃の生まれと推測される。