Alright, this rumor has been out there for a couple of weeks now and is gaining traction everywhere. Even though this is the Spoiler Thread, if true, this is REALLY a massive spoiler. It also ties back to the latest series of books and Luke Skywalker, in which Rian Johnson contributed to the story line.
Spoiler!
In the scene Luke tells Rey that the Jedi Council became “arrogant” and that they were hiding a “secret,” which led to their demise. The old Jedi master takes Rey’s hand and shows her a glimpse into the past. They see two children playing near a tree on an alien planet. The boy noticed that he had greater strength and intuition when he was closer to this tree. The girl noticed that the tree also made her brother increasingly angry. One day an argument breaks out between the children, and the boy kills the girl. The boy touches the tree and is “transformed,”. He kills his parents and leaves the planet. Meanwhile the girl is revealed to be alive, transformed by the tree as well, using her power to start the first Jedi Order.
The girl explains how The Force can be used for both good and evil. She tells her followers that one day she would return as either a boy or a girl, and that they should train this child. Luke tells Rey that the Jedi Order had been searching for The One (reincarnation of the original founder of the Jedi) for a millennia. When they found Anakin Skywalker and thought that he would bring balance to The Force, the Jedi were “deceived” and the Clone Wars were the result. The scene also shows Rey’s parents, and Luke is not the father. Luke tells her how she was identified as strong with The Force, and how she was supposed to begin her training, but never reached her destination for an unknown reason. In the scene Luke gives Rey a choice, and she has till sunset to make it.
Also, in other reports, the boy starts the Sith Order and the girl is the founder of the Jedi Order.