At some point in the 300 years of Targaryen rule, but we don't know when (he's mentioned, but not given a date). The worldbook gives all the original members of the King's Guard, and he isn't one of them:Idk why he was removed, He was there in lore, just as a kingsguard member instead of lord commander.
LC Corlys Velaryon
Richard Roote
Addison Hill (bastard of Cornfield)
Gregory Goode
Griffith Goode
Humfrey the Mummer
Robin Darklyn
I'm more annoyed that Harren the Black still has his daughter, despite being explicitly stated to be daughterless.