Birthname 古屋武治 (1925-1945).
Studying with 古賀政男, starting musical activity by the name of 古屋雅章 (1946-1948).
Then, he is officially adopted by 古賀政男 and then takes his lastname 古賀 and changes his firstname to 丈晴, 古賀丈晴 (1948-1958).
His composer name at King Records then is 古屋丈晴 (1958-1962).
When he got married with 山本富士子, she had no brother and he became son in law adopted child of 山本 family, he has been using this name since that time, 山本丈晴 (1962-).
(Source: Wikipedia ja:山本丈晴)