The "other" to which Yoda refers is Leia, who is Luke's twin sister, as we learn in this exchange between Luke and Obi-Wan in Star Wars: Episode VI - Return of the Jedi (1983) : Luke: Yoda spoke of another.
But the biggest reveal came midway through Empire when Yoda reveals to Kenobi that there 'is another'. And we learn that this other he speaks of is none other than Luke's own twin sister, Leia.
Originally Answered: Who did yoda mean when he said to Obi wan " there is another"? Retroactively, given what happens in Return of the Jedi, he was talking about Leia. As Luke's sister she had the same Force potential and might be the very last hope of the Galaxy if Luke should fail or fall.
Because of Yoda's self imposed exile, at the beginning of Star Wars: A New Hope, he is unknown to most of the Rebellion. For example, Luke was completely unaware of Yoda's existence until Star Wars: The Empire Strikes Back.
According to Reddit user Cheekywanquer, a line spoken by Yoda (Frank Oz) in the 1980 film predicted that Rey (Daisy Ridley) would play a huge part in the future of the galaxy decades before her introduction in 2015's The Force Awakens.
2019's 'Star Wars: The Rise of Skywalker' revealed Rey to be the granddaughter of Emperor Palpatine.
Master Yoda knew that Darth Vader was once Anakin Skywalker- the boy he sensed too much fear in to train way back in Star Wars: The Phantom Menace. For many years it's been assumed Master Yoda was aware from the day Vader gained his cybernetic enhancements and signature wheeze.
To teach Anakin responsibility, Yoda assigned Skywalker a Padawan learner: Ahsoka Tano. Yoda knew there would come a time when Anakin had to let go of Ahsoka.
Master Yoda has risen above all others to claim the top spot as the most powerful Jedi of all time and the true chosen one according to IGN's audience. He won pretty handily as well, as he was victorious in 89,756 of his 95,243 battles and had a win percentage of 94.2%.
After their battle in Star Wars: Revenge of the Sith, Palpatine was sure Yoda was still alive. So why did he never bother finding the old Jedi master? While everyone remembers Anakin's fight against Obi-Wan, the battle between Yoda and Palpatine was just as important.
George Lucas himself has stated that Anakin is the Chosen One and that the prophecy is true, although it had been misinterpreted by the entire Jedi Order. Lucas believes that both the dark side—greed— and the light side—compassion—are integral parts of human beings.
Luke struggles as he looks at the size of the spaceship, and Yoda speaks the immortal words, “Do or do not, there is no try.” Coaches, teachers and self-help gurus love to quote those words when trying to get their pupils to commit completely to something, but what if Master Yoda was wrong?
All his life has he looked away… to the future, to the horizon. Never his mind on where he was.”
Yoda also senses Anakin falling even deeper into loneliness. With the death of Obi-Wan, Yoda senses that the galaxy is rapidly becoming emptier and emptier. Yoda is then menaced by two more probe droids. Yoda uses the Force to summon lightning and destroy the droids.
The quiet Yaddle was a member of the same mysterious species as the revered Jedi Master Yoda. Yaddle sat on the Jedi Council with her fellow green-skinned diminutive Force-user. By the time of the Clone Wars, she was no longer on the Council.
The Last Hope was a Jedi starship which survived on Kesh for nearly four thousand years following the Great Calamity during the aftermath of the Hundred-Year Darkness.
Yoda. Yoda was a wise, experienced, and powerful Grand Master of the Jedi of an unknown species and the oldest known prophet in existence (having lived at least 900 years), considered the wisest and most powerful Jedi Master within the Star Wars universe.
Biography. Legend had it that Yoda—a Jedi who became Grand Master—was trained by N'Kata Del Gormo.
Unwilling to see his son die, Vader gave his life to save Luke, thereby dying as Anakin Skywalker. Anakin ultimately fulfilled his role as the Chosen One and brought balance to the Force, fulfilling Qui-Gon Jinn's belief in the prophecy that foretold Anakin's destiny.
The Prime Jedi was also the founder of the Jedi Order. The Prime Jedi established the Order on the planet Ahch-To, around 25,025 BBY. The first Jedi Temple, which was located on Ahch-To, contained a mosaic of the Prime Jedi in a state of meditation and balance.
Former Jedi Barriss Offee betrayed the Order — and led Ahsoka to leave Jedi behind, too. But why? While most Star Wars fans know that Ahsoka Tano left the Jedi Order, those who haven't watched Star Wars: The Clone Wars might not know the circumstances that led to her decision.
She eventually became the Padawan of a human male Jedi Master, Stellan Gios. Vernestra was enough of a prodigy that she eventually attained the rank of Jedi Knight at the age of only fifteen, making her the youngest Knight in a generation.
This is confirmed later in the movie when Obi-Wan informs Padme that Anakin killed them. Both are torn apart with hurt and confusion, trying to make sense of something so terrible.
Thus, while Qui-Gon was less powerful than Yoda, Palpatine feared him more.
Yoda didn't specifically know how this would go down, or to what degree Anakin would cause it to happen, but he was playing a much longer game by Revenge of the Sith, and that's at least, in part, explained by Yoda's Force connection with Qui-Gon's spirit.