Question: who is mulder's father on the x files
Answer: Information Occupation FBI Special Agent Family The Smoking Man ( biological father ) Teena Mulder ( mother ) Bill Mulder ( legal father ) Jeffrey Spender ( paternal half - brother ) Samantha Mulder ( maternal half - sister ) William Scully ( son ) Unborn Child Partners Dana Scully Affiliations John Doggett Monica Reyes Walter Skinner The Lone Gunmen Duration 1993 -- 2002 , 2008 , 2016 , 2018 -- Seasons 1 2 3 4 5 6 7 8 9 10 11 Films The X-Files , The X-Files : I Want to Believe