The Kinoshita family did not change its honsei (original name) until after the Meiji Restoration, when honsei (original name) and myoji (family name) were legally integrated into one, as the form which is seen today.
明治維新後に本姓と名字が法的に一本化されて現在見られる姓のあり方に統合されていくまで、木下家は本姓を変えることがなかった。