Soadrqm was, among other things, playing at the, eh, :A-face that has become associated with Jane, John's ectomom.
Dad is John's Guardian/adoptive father/half-brother. He is his no one's dancestor, as far as we know he isn't even an ectoclone but the only person in Homestuck that was conceived in a natural way. He is the last human, it's him.
ID/ETHEORIES:
-Dad's Col. Sassacre(time travel)
-Dad's adopted. His birthname in all universes was 'Brunner'
-Dad's the ultimate Gameconstant: If He dies, Paradox space rearranges itself to make him alive again
-(related)Dad is actually a clown; it's what's on the inside that counts
-Dad's actually Nepeta
-Dad's Col. Sassacre(eternal life)
-Dad is Fedorafreak; Godtier FF used a Skaian portal at some point and was duplicated
-Dad's not bald: his head is a cueball
-Dad's Col. Sassacre(it was a prank)
-Dad's actually a mediocre baker, but even he never ruins a cake with Betty Crocker's brand new convenience blend! One plastic toy in every box, buy a hundred NOW and get a pack of fruit gusher for FREE!
-Dad's not Col. Sassacre, but Sassacre's long-lived, extremely strong human-troll hybrid spawn. It was his birth that instilled such a abhorrence regarding human reproduction into the Batterwitch, he hung to Nanna more as an adoptive son than a little brother for decades due to his slow aging(while actually only a few months younger than her) after the witch vanished, and now the Condesce is keeping him alive for sentimental reasons. He is hiding malformed horns under his hat.
-Dad is actually a Denizen. It was under our nose all along!
-Dad is a true badass from an era long gone, and that is all that is to him.
-Dad is actually a midget on the shoulders of a second, and something taller, midget