WHO is Finn?

In Star Wars "The Force Awakens", we get a good idea of where stormtroopers actually come from. Finn has been stolen from his family as a young boy to be trained as a First Order Stormtrooper. Episode VIII is not far away, so we can start asking ourselves: who was his family?
What mostly guides us in speculations is the fact that Finn is black; there are a few well-known characters in the Star Wars universe that are, so we will be studying them.

Lando Calrissian

The first (and major) theory is that Finn is Lando Calrissian's son. Technically, it is possible because Episode VII happens 25 years or so after the battle of Endor, which is close to Finn's age. Lando may have had a baby just after the downfall of the Empire. Because he helped Leia and Luke escape from the Empire's grip in Episode V, we can assume that the Empire "blacklisted" Calrissian for his betrayal. While recruiting stormtroopers, the First Order may have chosen in priority the people who had been out of favor or betrayed the Empire. Let us not forget that Kylo Ren worships Darth Vader; he may have wanted to avenge his grandfather by taking the son of the man who had betrayed him (This could be the reason why Kylo Ren immediately thinks of Finn in the beginning of the Force Awakens, when Phasma asks who the rebellious stormtrooper is). Furthermore, we don't know wether Lando Calrissian is dead or not, we may see him in future movies.
To further support this theory, this jigsaw puzzle on the right was listed on amazon. The title indicates Finn is Lando's son, which is either a major clue, or just a mistake coming from a person who assumed Finn was Lando's son just because of the color of his skin.

No last names have been revealed for Finn or Rey, and director J.J. Abrams told Entertainment Weekly, “I will only say about that it is completely intentional that their last names aren’t public record.” 

We can assume that if Finn's last name is being hidden, it implies it's significant (same for Rey). 

Finn could also be the grandson of Master Jedi Mace Windu. That could explain the fact that Finn can decently handle a lightsaber. Sadly, this theory is highly improbable, for jedi are not allowed to marry, and Windu was the head of the Jedi Council.

Finally, could Finn be related to Captain Panaka from Episode I...? We shall see!