This has been a concept that Lucas himself wanted to include, but opted out, because it'd make Vader's choice in ROTJ between his literal dad and his son, instead of Palps being more like a darker "father figure" rather than a real dad.
"On Coruscant, PALPATINE completes his seduction of ANAKIN, who at first refuses to go over to the dark side-- until the Chancellor makes a startling confession:"
DARTH SIDIOUS-- "I have waited all these years for you to fulfill your destiny... I arranged for your conception. I used the power of the Force to will the midichlorians to start the cell divisions that created you."
ANAKIN-- "I don't believe you."
DARTH SIDIOUS-- "Ahhh, but you know it's true. When you clear your mind, you will sense the truth. you could almost think of me as your father."
ANAKIN-- "That's impossible!"
DARTH SIDIOUS-- "Nevertheless, you must decide."
Later this dialogue was cut, as you can see if you read on the second column, about halfway down on Page 60. It simply states this there
"The dialogue indicating that PALPATINE is responsible for ANAKIN'S creation has been cut."