My Rey background theory
Everybody is trying to figure out who Rey is and who left her on Jakku well here I go
The person who left her on Jakku is Kylo Ren/Ben Solo
This answers so many things just follow me. Rey's age is around 19, Kylo's is around 30
Rey was about 5 or 6 when left on Jakku this means Kylo/Ben would have been about 16 or 17
Set the way back machine to when Luke started the new Jedi School. Kylo as a teenager feels Luke is Holding him back some how he is seduced by Snoke. Snoke uses Kylo to wipe out the new Jedi school. Everyone believes this is why Luke goes into hiding because he lost all his students and the betrayal. I say No.
The real reason Luke goes into Hiding. Kylo kills all Luke's students but one, Rey is Luke's daughter or some blood relative. Snoke believes Kylo wiped out all Luke's student. Kylo however is still struggling between his light and Darkside. Can't find it in his heart to kill his cousin. She completely trusts Kylo because they have been raised together he even dotes on her. So instead of killing her he kidnaps her and hides her on Jakku.
Kylo then somehow tricks Luke into thinking he's Killed Rey, Presenting say A burned body of some sort. In his grief of losing his students and the shock of all that death Luke is unable to differentiate the Death of his daughter from the deaths of all his students in the force. This is what pushes Luke into hiding. He takes what he believes is Rey's remains and buries them at the first Jedi temple. Which is where we see him at the end of the Movie. The grave on the planet at the end of the Movie is not Lukes wife but Rey's Grave and he's been there ever since.
In order to hide Rey from Snoke, Kylo wipes her memory. This is for two reason one to protect Rey the other to hide his failing to kill her from Snoke. This makes all the conversations to Vader have even more reverence and also makes the scene with Han Solo so much more powerful because not only does he end the conflict of Light and Dark he finds Absolution for allowing Rey to live.
This also explains his reaction of the Statement of "What Girl?" If Snoke learns of his deception of keeping Rey alive. Smoke may dispose of him. Also it may even help explain the final fight a bit more between Rey and Kylo. He is holding back because he is remembering all he has sacrificed to try and keep her from Snoke that truly deep down he does not want to kill her and therefore the Light is still in him.
So anyway that's my theory what do you all think?