Now I've already seen plenty of speculation of who his father might be, some being so ridiculous as to "Watto" being the mans father.
(come on. Watto, really, how stupid are you)
but what people aren't remembering is that
Palpatine/Sideous told Anakin that Darth Plagueis, could save/create life out of absolute "spontaneousness"
If we were to reflect back on "episode I the phantom menace", Schmi Skywalker did not know how she got pregnant, which we can only put two and two together on this one.
Anakin had the most purest DNA for being a Jedi, with high concentrations of the Midi-Chlorian (Jedi DNA) in his blood
Plageueis was easily the strongest on the dark side of the force (maybe even the light too depending on the time line)
for someone to be that strong with the force would be bound to create a child that easily has just as much strength and potency of the force in his blood (again I remind you that his DNA was so pure with "Midi-Chlorian" that no other Jedi has had that much in their DNA)
Maybe also because Darth Plagueis was of the dark side could reflect on why Anikin was so easily agitated and could easily get so much anger and hatred. (It is against the Jedi code to fight with any sort of anger or hatred)
I'm going to end it here, this is why I think Anakin Skywalker is spawn from Darth Plagueis.