Through a vision in the Force, Jedi Master Obi-Wan Kenobi thought Owen was his sibling. The truth is that Kenobi was actually seeing Owen Lars, who happened to be Anakin Skywalker's stepbrother.
Obi-Wan Kenobi was born to parents on Stewjon; however, because of his Force-sensitive nature, he was brought to the Coruscant Jedi Temple as a baby. There, the Jedi Order trained him in the ways of the Force. While apprenticed to Jedi Master Qui-Gon Jinn, Kenobi began to have dreams about his parents and a brother named Owen. Jinn told him that these dreams could be visions of the past or future. Kenobi spent a large part of his life before the Clone Wars believing that he had returned to Stewjon as a child, met his parents, and formed memories of them and his brother.
Kenobi found out only a few months into the Clone Wars that his Padawan, Anakin Skywalker, had encountered his stepbrother on Tatooine before going to Geonosis. After Kenobi heard about Lars and the death of his mother, Shmi, he started to doubt who his brother Owen really was. It wasn't until the Clone Wars ended and the Order was destroyed that Kenobi started to piece together this puzzle that had been around for decades. While fleeing persecution on Nar Shaddaa with the baby Luke Skywalker, Kenobi got ready to take the boy to the Lars Homestead on Tatooine. Kenobi finally realized that the dreams he had as a boy were a vision of Owen Lars, his student's stepbrother. He felt a true connection with Owen, in a way. Since Kenobi felt like his former student was a brother, Lars would also be his brother.
The idea that Obi-Wan Kenobi and Owen Lars, Luke Skywalker's adoptive uncle, were related as brothers was in the script for the 1983 film Star Wars: Episode VI Return of the Jedi, but it was cut from the final version. However, the movie's novelization did have a line where Kenobi called Owen "[his] brother." Similarly, The Essential Guide to Characters stated that Kenobi "does have at least one brother, Owen Lars," and Owen Lars was clearly called the "brother of Obi-Wan Kenobi" in the Premiere Limited set of the Star Wars Customizable Card Game that Decipher released in 1995. The novel Jedi Apprentice: The Hidden Past from 1999 also hinted at this brother named Owen in one of Kenobi's dreams. However, the 2002 movie Star Wars: Episode II Attack of the Clones revealed that Luke's uncle was Anakin Skywalker's step-brother, not Kenobi's brother. Abel G. Peña's short story "Lone Wolf: A Tale of Obi-Wan and Luke," which was released online in 2015, explained that Kenobi's dreams were a vision of the future instead of a memory of the past.