Original Pre-Crisis Alfred came to the service of Bruce Wayne after he had long since become Batman. Even Robin was already around. He was the son of Jarvis who had served the Wayne family and came to Wayne manor at the dying wish of his father.
Alfred started off fat and clean shaven but his appearance was altered to match that of the Alfred who appeared in the 40's Batman serials.
In the 60's Alfred was killed off and a few years later revived but transformed into the villainous Outsider. Eventually he was cured and returned as the Wayne Butler.
Post COIE Alfred was retconned to have been the Wayne family butler for Bruce's whole life and raised Bruce after his parents were killed.
Time as a stage actor and in millitary intelligence have been the in the backgrounds of both versions of Alfred right from the beginning.
Alfred possibly being Bruce's biological father is recent stupidness from the mind of Grant Morrison.