Spoiler: Kylo Ren
Kylo Ren is a Solo but he doesn't know it. Not Leia's son, Han's from a previous relationship before he met Leia. His mother is killed by Rebel soldiers during the battle on Tatooine. Kylo thinks they murdered his mother and he found out the leader of the Rebels at the battle was Han Solo. (This is why he kills Han in the way Jason Ward has already described.) After the battle he discovers he has control over the Force and falls to the Dark Side. This will all be explained in a lead up comic that will be released after TFA. Driver's age is not the same as his character's. His face is never shown in TFA. Kylo earns his Darth title after killing Solo, Darth Exsito (based on Latin for awaken).

Spoiler: Rey
Rey's real name is Kira Organa. She is Han and Leia's daughter but she was born after they spilt, Han didn't know Leia was pregnant. Han and Kira do not know each other. She has been on Tatooine as a Rebel scout using Rey as an alias. She works closely with a former bounty hunter who joined the Rebels, Major Ematt (played by Max von Sydow). Kira is Luke's last remaining apprentice. Jason ward described what happened with Kylo as a flash back scene. It will actually be in the kylo comic book I mentioned earlier. Kira is the "Leia" of the trilogy.

Spoiler: Max von Sydow
Ematt will be the focus of one of the spin-off movies but will be played by a younger actor during this time pretending to be Boba Fett after the real Boba died in the Sarlaac. Ematt is killed by stormtroopers. By the way, the names revealed by Jason ward are legit.

Spoiler: Finn
Finn is not related to any OT or PT characters. His full name is Brance Finntan but goes by Finn. He will become an apprentice of Luke's in Ep 8 after he learns he can use the Force. He falls for Kira. Finn is the "Luke" of the trilogy.

Spoiler: Domhnall Gleeson and Greg Grunberg
Gleeson is portraying Byron Skywalker, Luke's only son. Byron is not a force user but he is skilled in combat. He is secretly working for the empire under the guise of Wenro Lennox. The Rebels captured an imperial commander and Byron is using a face mask similar to the one Obi-Wan used in the Clone Wars to impersonate him. While in disguise he is portrayed by Greg Grunberg. Skywalker's mother is never mentioned.

Spoiler: Maisie Richardson-Sellers
Maisie Richardson-Sellers is Korr Sella as rumored. She will be working for leia but will die in this movie.

Spoiler: Luke's scenes
The last scene with Kira giving Luke the lightsaber is in the movie but it's not the first time we see him in the movie. Luke will have a battle against Kylo Ren and arrives just before he kills Kira and Finn. Kira is unconscious when Luke arrives so when she gives him the lightsaber it is the first time they share the screen together. Luke wounds Kylo but he escapes.

Spoiler: Andy Serkis
Serkis is Kylo's master. His name is not revealed in the movie but he is an alien Sith Lord of a new species. His only scenes are near the beginning of the film saying the lines from the trailer to Kylo and when Kylo reports in after killing Solo. His role is bigger in later films. Serkis will cameo as a rebel pilot with cybernetic implants named Gorwyn. He will die in the scene shown in the trailer with the X-wings like Porkins in A New Hope.

Spoiler: Poe Dameron and BB-8
Poe Dameron is "Han" of this trilogy. Has cool vibe about him and gets the ladies. He looks at Kira as a sister though since he has known her since she was a child. He is very protective over her when he figures out Finn has the hots for her. BB-8 doesn't belong to Poe but is with him in the beginning of the movie. BB belongs to Kira.

Spoiler: Lupita Nyong'o
Lupita Nyong'o is portraying a new alien species and will be gci with some practical effects as previously mentioned. Her name is Rosetta and runs the Cantina near the Rebel's base but she has 2 roles. The second is Leia's political rival pushing for building a new "death star" to eradicate the empire once and for all. Her name is senator Jules Markkuns and a human.

Spoiler: Captain Phasma
Amy Beth Hargreaves is captain Phasma, the chrome trooper. She leads the empire's squad of shock troopers. She uses a lightsaber but isn't a Sith or Jedi. Similar to Grievous. She gets killed by Byron Skywalker.

Spoiler: Gwendolyn Christie
Crystal Clarke, pip Andersen, Christina Chong, and the guys from The Raid (Iko Uwais, Yayan Ruhian, and Cecep Arif Rahman), are all a part of a sect of gray Jedi who meet Luke at the end of the movie and join his cause to defeat Kylo Ren. They are led by Gwendolyn Christie (a Twi'lek, she's not given a name at this point) she will have a bigger role in the next movie. They will betray Luke in Episode 8 because they are loyal to Kylo's master.

Spoiler: Leanne Best
Leanne Best is a Rebel admiral named Relyk and will be the same species as Ackbar but they're not related.

Spoiler: Miltos Yerolemou
Miltos Yerolemou is a Rebel captain named Trilla who fights Kylo but is easily killed.

Spoiler: Billie Lourde
Billie lourde is Kira's sister Drienne Solo, born before Han and Leia's separation. She is a Rebel leader.

Spoiler: Warwick Davis
Warwick Davis took over for Kenny baker in the R2-D2 role part of the way thought production but also cameos as a musician leading the band in Rosetta's cantina.

Je tient juste à préciser que Byron Skywalker ça pète comme blaze

source http://thecantina.starwars7news.com/index.php?threads/info-on-all-the-actors-characters.2001/