During Star Wars: The Phantom Menace, Darth Maul had no clue about Anakin and dismissed him as a child following the Jedi around. But with Maul's return during the Clone Wars, he likely found out about Anakin through his obsession with Obi-Wan.
Maul always knew. He figured it out before everyone else. He even staged a massive war on Mandalore with the sole intention of luring Anakin and Obi-Wan there. Maul saw through his former Master's plan, realising that Anakin was the apprentice Sidious sought.
In a non-canon story from the pages of Star Wars Tales #9, Darth Maul was resurrected to fight Darth Vader to the death. Ultimately, Darth Vader was named the victor for a pitch-black reason: He hates himself more. In the main Star Wars canon, Darth Vader and Darth Maul never met, let alone fought.
Very few people knew that Darth Vader and Anakin Skywalker were the same person up to his death in 5 ABY. Imperials who knew in the current canon: Sidious (emperor), Grand Moff Tarkin, all or most of the Inquisitors, Grand Admiral Thrawn, various clones in the early empire.
Yep. Darth Maul didn't really say or show straight up that he "feared" Darth Vader, but he openly stated his belief that he could not defeat Darth Vader without the help of the Jedi, therefore on his own.
R2-D2 was present when Padmé gave birth to Leia and Luke, so he knew Luke was Anakin's son – but what he didn't know was that Anakin became Darth Vader. In addition to that, Anakin's fall was surely a painful event in R2-D2's life, one that he definitely wouldn't like to remember or even talk about.
Yoda. Yoda's knowledge of Luke Skywalker's true parentage was also confirmed in Return of the Jedi. As with Obi-Wan, Yoda believed that Anakin's fall to the dark side made him unsalvageable, with the Darth Vader persona being his only identity following his ascension to Sith Lordship.
The fight was orchestrated by a darksider cult called the Prophets of the Dark Side, who wanted Vader killed and replaced with Maul as Darth Sidious' only true apprentice, because they felt the former was "tainted" by his Jedi past and not worthy of being a Sith.
Ahsoka asks what he wants with Anakin Skywalker. Maul says that Skywalker is the key to everything. When Tano asks if it is to bring balance to the Force, Maul replies that Skywalker is the key to destroy and that he has long been groomed for his role as his master's new apprentice.
By the time of Episode 3; Anakin is in his prime, and already one of the Jedi Order's most powerful “masters” (although technically still a knight), just behind Obi-Wan, Windu, and Yoda. Maul wouldn't stand a chance. Anakin stomps.
Obi-Wan Kenobi was Darth Maul's nemesis in Star Wars, but there was a time when a young Anakin Skywalker dueled and defeated the Sith Lord. Before the Clone Wars forced them into military positions, Star Wars' Jedi filled many roles for the Republic.
Maul always knew. He figured it out before everyone else. He even staged a massive war on Mandalore with the sole intention of luring Anakin and Obi-Wan there. Maul saw through his former Master's plan, realising that Anakin was the apprentice Sidious sought.
The sequence calls back to a similar scene in Revenge of the Sith, when Bail Organa orders Threepio's memory be erased to prevent him from sharing information about Anakin Skywalker's fall to the dark side.
Darth Vader acts like he doesn't even know C-3PO or R2D2. They were with him since he was a child. He did everything he could to forget his past. Also, his plating had been replaced many times, and protocol droids all look very similar.
In this version of events, R2's deux ex backup goes deeper into C-3PO's storage banks and reawakens his entire memory from the initial switch-on by a young Anakin in The Phantom Menace.
Leia's Force abilities and her lack of awareness of her true identity also contributed to Vader's inability to sense their familial connection. Vader's denial of Anakin Skywalker's legacy and his fear of getting hurt again prevented him from realizing the truth about his children until later in the original trilogy.
Darth Vader didn't learn he had a daughter until Return of the Jedi, when he stood before Emperor Palpatine. The Emperor's power probed Luke's mind, attempting to goad him to fall to the dark side, and he discovered Leia's existence. "Sister," the Emperor taunted.
In Star Wars Legends Leia was visited by the force ghost of her father Anakin Skywalker, the man who used to be Darth Vader. It wasn't a pleasant meeting as Leia was unable to forgive him for the things he'd done no matter how hard he begged, and it was the only time she saw him.
Padme's death fuels his rage, and his rage dictates his actions. It is only when he saw Luke, when he lost his anger for a second and felt his love for his son.
