There's a slim chance that Steve Fox and Jin Kazama could be brothers...

I't very possible because Steve does sort of look like a cross between Nina (Minus looking like a girl) and Kazuya. It is very possible.

Okay, here's an idea...

Heihachi still didn't know of Jin at that time, so he thought if Kazuya were to have a son, maybe that son could inherit Kazuya's powers.

And seeing that Nina was a strong woman, Heihachi probably figured that she would be perfect as a mother of Kazuya's cursed child.

But when Steve was born, Heihachi found out that there was nothing special about him, so he decided to throw the baby off another cliff. That's one of Heihachi's talents... throwing kids off mountains...

That would explain Steve's scars. Steve never knew were those scars came from.

Jun Kazama was probably already pregnant at that time, so that's why Devil chose Jin over Steve. Plus, there was nothing artificial about Kazuya banging Jun.

quote arseball

Erm, Steve Fox is an actual boxer in the merry country of England.

Erm, Steve Fox never knew where he was from... Oh, and by now, we should all have figured out the obvious fact that Steve Fox is Nina's son.

EDIT: Oh wait, you're talking about the actual boxer?

steve fox IS ninas child. and he needs a daddy - so i think kazuya is his dad.
i have the german version of the game and in this version heihachi said at steves storieending "we are lucky that a killer singed steve, turn this to our advantage and turn him over to the killer". so i think he should have been murdered as he was very very young and so he got the scar on his arm. in the american version heihachi does not mention the scar.

quote Optimus Prime

Or maybe Kuma...?

Kuma?! Ok, I can understand Paul being the father, but a bear? No. It wouldnt make any sense.

alright alright lol I got ya. My guess would be a main character as it would make no sense to make a side character the father. But thats just my opinion, take it for what you wish:D

Paul Phoenix? Hmmm, interesting... But I highly doubt it though.

Heihachi wouldn't have much use of him if he were Paul's son. Heihachi's after the devil gene, remember?