There are many theories as to the lineage of Rey in Star Wars the Force Awakens. Some believe that she is the daughter of Han Solo and Leia Organa, while others strongly believe that she may be the daughter of Luke Skywalker. While the later would make sense, why didn't Luke act more excited when seeing Rey after all of those years. My guess is that maybe she isn't the daughter of Luke Skywalker after all.
In the original movies, George Lucas created the story line to revolve around the Skywalker family. George Lucas stated that the six films he created were about Anakin Skywalker's fall to the dark side of the force, and then his redemption thanks to the help of his son Luke Skywalker.
I'm sure that in these last three films (Episodes VII, VIII and IX), we would have seen more of Luke Skywalker's bloodline if it were up to George Lucas. However, George made it clear that Disney had it's own ideas with regards to how the last three films will play out.
My guess is that Disney wanted to do something different, but also wanted to include some of the old nuances of the original films. They apparently decided that the new bad guy in the film known as Kylo Ren (Ben Solo) would be a member of the Skywalker family on Leia's side, but would be the primary antagonist in these last three films. My guess is that these films will be centered around Ben Solo's character's development throughout these three films. In other words, it will revolve around his constant battle between the good and evil that lives within him. We all saw his emotional fight between the dark and light side of the force.
There were several instances throughout the film where the light side of the force controlled his actions. Instances such as not killing Poe when he had the chance. He had the perfect opportunity to kill Poe after he received the information on where to find BB-8.
He then showed weakness when he didn't kill the First Order officer that broke the news about Rey and BB-8's escape from Jakku. If it were Darth Vader receiving that information, he would have choked that officer to death.
His final show of weakness was when he didn't kill Rey when he had her captured on his ship. If he knew that she was strong with the force, why didn't he just kill her. Instead he takes his helmet off and talks to her like a normal person.
My guess is that Kylo Ren (Ben Solo) will slowly come back to the light side of the force over the next three films. His redemption will come at the hands of Rey. Which brings me back to her lineage. I have a strong believe that Rey is not related to Luke Skywalker. Instead, she is the daughter of another Jedi Master that we have already seen.
First lets remove the thought of her being Luke's daughter. This is not the expanded universe. In the expanded universe, Luke changed the rules of the Jedi and took on a wife (Mara Jade). If Disney is not going to follow the expanded universe, then my guess would be that they are going to stick with the original teachings of the Jedi. if that is the case, then Luke will have continued to follow the original teachings of the Jedi order meaning that he would not have taken on any personal attachments like a wife or child. We know that Luke reorganized the Jedi order and started a new Jedi Academy. It is possible that Rey may have been a padawan at his new academy which would explain her knowledge with the lightsaber and being able to use mind tricks. According to various reading material, Rey was 5 years old at the time she was taken and dropped off on the planet of Jakku. She was probably taken from the academy either just before or after the Knights of Ren came and destroyed the new Jedi order. Being strong in the force and a formal Jedi padawan, she had to be protected from the Knights of Ren and anyone else that were a threat to the Jedi. If she were truly Luke's daughter like everyone else seems to believe, Luke would have taken her with him when he fled to his Island retreat. After all, she would have been well protected and well trained in the ways of the Jedi by her father. Since she was left on Jakku, I feel as though she was related to a different Jedi Knight all together.
Now comes my theory on who her father may be. I feel that Rey could be the daughter of Jedi Knight Caleb Dume better known as Kannan on the television series "Rebels". Kannan was a padawan that trained under the Jedi Master Depa Bilaba. At the time of Rey's birth which was 11 years after the Battle of Endor, Kannan will have been 47 years old. Still young enough to father a child. We all know that Kannan did not follow all of the rules of the Jedi order, so for him to fall in love and help to conceive a child was very possible. In the series "Rebels", he was in love with a Twi'lek known as Hera.
Since Rey is a human child, my guess is that Hera must have died sometime between the "Rebels" series and the time of Rey's birth. Which means Kannan would have had to of met another human female and fall in love. Since kannan had a crew who he became very close to, it is very possible that he may have fallen in love with his other female crew member known as Sabine Wren.
At the time of Rey's birth, Sabine would have been 35 years old. Although she was 12 years younger than Kannan, their relationship could have been a real possibility. (After all, I am currently 48 years old and my wife Alisha is 36.)
Kannan and Rey both seem to study the same lightsaber form (Form 3).
Here is a photo taken from the series "Rebels" showing Kannan in a Form 3 stance.
Here is a photo of Rey in a Form 3 stance.
You can definitely see the resemblance in both of their stances.
With the fact that Kannan didn't follow the original teachings of the Jedi order and was able to fall in love, and the fact that both him and Rey are both strong with the force and studied the same lightsaber techniques. I have a strong feeling that Rey may actually be the daughter of Kannan.
As for Rey being the daughter of Sabine, I feel that Rey possesses the same spunkiness that Sabine had in the series "Rebels". Not to mention Sabine was a Mandalorian weapons expert, and new her way around a ship. Which could be why Rey is good at using various types of weapons (blaster, staff and lightsaber) and knows how to fly and work on ships.
If Rey is the daughter of Kannan or another Jedi Knight we have not seen as of yet, it is very possible that Rey may be the Mara Jade to Kylo Ren's (Ben Solo's) Luke Skywalker. In the expanded universe, Mara Jade was known as the "Emperor's Hand". She worked for the Empire and was once tasked with hunting down and killing Luke Skywalker. In the end, Luke and Mara fell in love and had a son. Since that story was part of the expanded universe, it no longer exists. However, what is to say that Disney decided to turn that story around and have Kylo Ren acting in Mara Jades place and Rey acting in Luke Skywalker's place in the new story.
We may see both Rey and Ben build on their relationship throughout the next two films, which will lead to Ben betraying Snoke and dismantling the remnants of the First Order.
In the end, Ben's betrayal to Snoke and Snoke's eventual demise at the hands of Ben and Rey, the Skywalker legacy will have once again been fulfilled.