With the new revelation of Han Solo's first wife Sana, I came up with a new theory, of course. I think that Finn and Rey are twins.
Here are my points:
Okay, to start out, Rey. Rey is obviously Han Solo and Princess Leia's daughter. She looks like them both and is described as solitary and independent. That is like Leia and Han.
Next is Sana Solo. Sana is Han Solo's first wife, and as you can tell by the picture she is black. Finn to is black. I think it makes more sense for Finn to be the son of Han and Sana Solo. Also It seems that Han takes more of a liking to Finn then Poe Dameron, the dashing X wing Pilot. Maybe love for his long lost son.
Now this could help the Sequel Trilogy be more like the Originals. Luke and Leia were twins, both children of another major character, Darth Vader. Now they could make it so there are two main characters, out of three, that are once again twins. Finn and Rey could be the Luke and Leia of the new trilogy. I think this would be interesting to see, especially since Kylo Ren is also of the Solo lineage. Supposedly Finn's family was killed off. Maybe Finn's mom, Sana, was killed because she did something bad to the First Order. It would be cool if there was a Mixed race set of siblings would be an interesting addition to the Star Wars universe. If Finn isnt Solo's kid from Sana, i think he is Zare Leonis's kid, from Rebels episode Breaking Ranks. That makes a lot more sense than the Calrissian's son theory.