Yoda knew and probaly told Obi-Wan. Darth Vader knew and possibly Thrawn if the book Outbound Flight is cannon. Also Tarkin might of known since he was friends with Palpatine before he became Emperor. Darth Plagueis.
Both Obi Wan Kenobi and Yoda had their doubts about Palpatine, but neither could sense the he was a Sith Lord. This because Palpatine had the ability to greatly cloud the Jedi senses. And surprisingly, Anakin never seemed to get this either.
Sidious, born Sheev Palpatine, was trained in the dark side of the Force by Darth Plagueis. Eventually, Sidious took on his own apprentice, Darth Maul, and killed his master.
Indeed he did. Dooku (aka Darth Tyrannus) knew his master's identity. At this point the Jedi thought Dooku was the Sith Master. The kidnapping was planned to reinforce public support for Palpatine while further confusing the Jedi about his true identity.
Thrawn definitely knows and Vader knows he knows. In terms of Palps, Tarkin knows Vader is Sith, they talk about using the force in ANH, when Vader chokes Tagge.
Who Knew Palpatine Was Darth Sidious - Star Wars Explained
Did Thrawn realize that Vader is Anakin?
Thrawn learned that Anakin Skywalker and Darth Vader were the same person during a mission with Vader, but kept the secret to himself. Thrawn's knowledge of Anakin's history explains his surprised reaction to hearing his name in Ahsoka episode 7 and likely gives him an advantage against Ahsoka Tano.
With that said, it's almost certain that Dooku did know the truth about the Chancellor, and that the criticism and kidnapping was all part of Dooku's act to foster war within the galaxy. In Revenge of the Sith, the "captured" Palpatine eggs Anakin on to kill Dooku, prompting a look of betrayal in the Count's face.
Following Qui-Gon's death by Maul's hand on Naboo, Dooku visited Palpatine in distress about his apprentice's death, hoping to have one day made Jinn an ally while also directly stating he knew of Maul's existence.
Thus, while Qui-Gon was less powerful than the likes of Yoda and Mace Windu, Palpatine feared him more. In the simplest terms, he was a wild card, and with the Sidious executing an intricate decades-long plan to seize power and destroy the Jedi, a wild card was something he just couldn't afford.
Supreme Leader Snoke #1 showcases Ren's training under Snoke, who subjects Ren to various physical and mental torments in order to foster his anger and strength in the dark side of the Force.
Even in the old Star Wars canon, the two had a confrontation, as they met in the comic book Star Wars Tales #9, where Maul pieced together that Anakin was Vader.
A Sith Lord with the ability to cheat death and create life, Plagueis is the enigmatic mentor of Sheev Palpatine / Darth Sidious, who, in accordance to the Sith's Rule of Two, eventually betrays Plagueis by murdering him in his sleep, taking his place as Sith Master.
Palpatine used his powers to hide his true nature from the Jedi, utilizing Force Concealment to completely hide his presence in the Force while clouding the Force for the Jedi. The Clone Wars also kept the Jedi busy and weakened, preventing them from realizing his true identity.
Sidious revealed to Maul that he did not intend to kill his former apprentice, as he still had use for Maul; it was Sidious' hope that Maul would lead the Sith to Mother Talzin, Maul's mother and the leader of the Nightsisters, so she could be eliminated as a potential threat to the eventual Sith rule of the galaxy.
What we do know is he knew that the clone wars would happen, he says that in the clone wars. This means that he most probably knew about the clones and order 66. He doesn't know about anikin until about a week before order 66.
Why didn't Count Dooku have a Sith name? He did have a sith name it was Darth Tyranus. However Count dooku was quite different compared to the other sith in the fact that he didn't really submerge himself fully in the dark side and that's why he never had sith eyes.
He also knew that Anakin had been corrupted by the dark side of the Force, and he wanted to spare him from any further suffering or guilt. By not saying anything when Anakin was about to execute him, Count Dooku showed mercy towards his former apprentice and allowed himself to pass away with dignity.
While Dooku may be powerful enough to hide his Sith eyes, there is another reason for his unusual appearance. Dooku's eyes were never yellow because he did not have the same motivation and emotions as other Sith. Dooku was an idealist who left the Jedi because he thought they had lost their way.
Then Dooku would soon plot his plan to betray Sidious and destroy him. Asajj Ventress would continue to get stronger and aid Dooku in his effort to take Darth Sidious's place. It was Dooku's plan all long.
But from Count Dooku's point of view, he believed that the cycle would continue and that one day he would dethrone Palpatine and take his spot. That only happens when an apprentice feels strong enough to challenge their master, and it's possible Dooku felt this during Star Wars: Attack of the Clones.
