Your Sifu (師父)is your direct teacher, the one you started under, the one that opened the door and let you enter into the world and life of the Chinese martial arts.  This is opposed to a Sifu (師傅), meaning “master” or “qualified worker,” someone who has attained a high level of skill in a particular craft.  You may address this master as “Sifu” 師傅 to show him respect, but this doesn’t mean he’s your personal Sifu 師父.  Even though both words are pronounced the same, their meanings are different.  Without your father, be it your Sifu or your biological father, you will not have life.  In that sense, you look at your martial art teacher as a father figure bringing you into the martial arts.