Sidious broke the Rule of Two at least twice: once by training Darth Maul while still under the tutelage of Darth Plagueis; and secondly, by taking on two apprentices at once, and in the form of two Jedi: Count Dooku, the former Padawan of the legendary Jedi Master Yoda, dubbed Darth Tyranus, and the Fosh Jedi Vergere.
Palpatine had 3 apprentices in canon. These were: Darth Maul, Count Dooku, and, of course, Darth Vader. Darth Maul was Palpatine's first apprentice. While he was still apprenticed to Darth Plagueis, Sidious found Maul on Dathomir and trained him in the use of the double-bladed lightsaber.
Darth Tyranus
The second of Sidious' mainstream apprentices, Darth Tyranus debuted in 2002's Attack of the Clones. Played by the singular Christopher Lee, Tyranus — AKA Count Dooku — is a very different brand of apprentice from Phantom Menace's Darth Maul.
The Rule of Two created a powerful dynamic by limiting the Sith to only one master and one apprentice at a time, although not all Sith followed the rule as some took apprentices of their own while still serving a master.
Sidious rarely used these elegant weapons, preferring to manipulate events indirectly and in secret. He wielded two lightsabers against his renegade apprentice Darth Maul and Savage Opress on Mandalore, took up arms to battle the Jedi on Coruscant, and used one of his crimson blades against his enemies on Ryloth.
DARK SIDE FRIDAY - Did you know Palpatine feared Qui-Gon Jinn? Palpatine was immensely powerful and he could see the future which made him very confident about pretty much anyone who stood against him.
Darth Maul was the first Sith apprentice of Darth Sidious. Sometime before the Invasion of Naboo, the Sith Lord Darth Sidious was trained by Darth Plagueis. Together they sought to achieve immortality and control the galaxy as equal rulers of a new Sith Empire.
The Sith remained hidden for a millennium, allowing the Jedi to believe that their ancient nemesis had gone extinct. The Sith stayed in hiding for a thousand years, their survival unknown to the Jedi, as they continued their revenge against the Jedi through Bane's Grand Plan.
As part of the Rule of Two, Bane took on an apprentice, Darth Zannah, to whom he passed on his teachings. Zannah escaped the notice of the Jedi Order.
Apprentice of the Dark Lord
Under Sidious's tutelage, Maul trained as a Sith apprentice, Sith warrior, and Sith assassin, eventually being given the title "Darth Maul." For years, Darth Maul was trained to become a weapon of the Sith.
Dooku voluntarily left the light side behind and became Darth Sidious' dark side disciple, taking the secret name Darth Tyranus and leading the Separatist army.
The term "Sith Lord" generally encompassed members of both sexes, although some female Sith such as Lumiya, Tahiri Veila, Olaris Rhea, and Vestara Khai were styled Sith Lady.
Eventually, another three-eyed child, Triclops, was born. Rumor had it that his mother was Palpatine's Umbaran aide Sly Moore, who had impregnated herself using DNA from an undisclosed source.
Kylo Ren, the leader of the Knights of Ren and formerly the Jedi Ben Solo, was never directly trained by Palpatine, but his tutelage under Palpatine's proxy, Snoke, was secretly orchestrated by the Dark Lord.
As the first Dark Lord of the Sith, Ajunta Pall founded the first Sith Empire and expanded it onto other worlds. The Sith took over the planet Ziost and created it as their capital and as Pall's new home. Pall eventually died after serving the Empire for many decades, but his Empire lived on.
Ahsoka Tano, a Togruta female, was the Padawan learner to Anakin Skywalker and a hero of the Clone Wars. Alongside Anakin, she grew from headstrong student into a mature leader. But her destiny laid along a different path than the Jedi.
Darth Plagueis was a legendary Dark Lord of the Sith trained by the Sith Master Darth Tenebrous.
After the Sith were decimated by the Jedi Knights of a thousand years ago, Bane enacted the Sith rule of two: there would be only two active Sith at one time -- a Dark Lord to embody the power, and an apprentice to crave it.
Darth Sidious was able to cheat his upcoming death by transferring his spirit into a clone body while falling into the reactor core of the second Death Star. He later sought to prolong his existence by futilely manipulating his grandchild Rey into killing him so he could live further by possessing her body.
Could a Sith live forever? Yes a Sith Lord can, and already has. Darth Andeddu created the Dark Rituals to transfer his essence from body to body to ensure eternal life. He was ultimately killed by his followers but he lived hundreds of years before that murder.
The average lifespan for a Sith, without any assistance from medical technology, is around 250 years. Taking into account that Force sensitive beings have extended lifespans, most Sith can reach up to 400 years.
In non-canon material it is said that Palpatine had a number of concubines and never took a wife in fear that he would produce a legitimate heir. One of these non-canon concubines was Roganda Ismaren, a former Jedi who survived Order 66, and lived for a time at Palpatine's side.
Mission to Mathas. Padawan Windu was trained in the ways of the Force by Jedi Master Cyslin Myr.
The youngest Jedi to ever be appointed the rank of Master is Mace Windu. Mace Windu was granted the rank of Master and offered a seat on the council at the age of 28. He was exceedingly powerful, quickly gaining status as somewhat of a 'champion' of the Jedi Order.
Mace Windu surely struck fear into Palpatine during their epic duel in Revenge of the Sith, and 472 Star Wars fans think nobody else surpassed that.