Both characters are from the Star Wars universe: The Son on the left and the Grand Inquisitor on the right. Both were also dark-side Force users, and both also died by Jedi lightsabers.
Son: First appeared in the Clone Wars.
http://starwars.wikia.com/wiki/Son/Legends
http://www.starwars.com/databank/son
Grand Inquisitor: First appeared in Star Wars Rebels.
http://starwars.wikia.com/wiki/Grand_Inquisitor
http://www.starwars.com/databank/the-grand-inquisitor
The Son was not a Sith but was simply a dark-side Force user. Anakin Skywalker killed him with a single impalement of his lightsaber after the Son's Father began to die. When the Father died, his body vanished. Not so with the Son's, but neither with the Daughter's either for that matter. Then the area began to collapse with falling debris as soon as the Father vanished, and Anakin was not able to confirm the Son's death too due to suddenly reappearing on his ship. (It's always good to double-check a bad guy's death!) Thus, my speculation is that the Son survived much like Darth Maul survived being cut in half, and returned much later in Episode VII to be the villainous, zombie-like Snoke, also not a Sith but merely a dark-side Force user. The more you look at the two, the more they look alike!
Update: This speculation was fun, but I think this is another case of "separated at birth." While they do look similar and have similar backgrounds, the Son hailed from Mortis in Wild Space, a region "south" of the "southern" Outer Rim, whereas Snoke hailed from the "western" Unknown Regions of the galaxy. It's too different. So we'll have to see what the Star Wars gurus have up their sleeves for Snoke's mysterious origin. [9/18/2017]
