Umbrella Academy: Why The Show Cut Luther & Five's Secret Link
In the Umbrella Academy comic books, it's revealed that Five and Luther are related, but the Netflix show has yet to mention the connection.
Season 2 of The Umbrella Academy chose to omit a connection between Five and Luther that was a big reveal in the comics. In both media, the titular Umbrella Academy is a group of reluctantly superpowered individuals who fought crime together in their youth under the supervision of their extraterrestrial foster father. In their malaise-ridden adulthood, they are repeatedly brought together to avert apocalyptic disasters which often revolve around their most volatile and powerful member, Vanya.
The origins of the Umbrella Academy date to 1989, when Sir Reginald Hargreeves adopted seven children from all over the world who had no obvious relation beyond their mysterious origin, all being born at exactly the same time to women who were not pregnant. The Umbrella Academy then spent the beginning of their superpowered lives as foster siblings before dire circumstances (including Ben's death and the disappearance of Five) drove them apart, only to reunite years later at Hargreeves' funeral. However, certain ties bind some members of the Academy together more strongly than others.
In the Umbrella Academy comic books, it is revealed that Luther and Five are twins, making them biologically related, unlike the other members of the Umbrella Academy or any of the other known superpowered people. As the two are fraternal twins, the fact that they are brothers could be kept secret until the Dallas arc, when Carmichael, the goldfish, professes his knowledge of it. So when the Handler eats the aquatic Temps Commission chairman in season 2, the Netflix show seemingly rules out the possibility of Five and Luther coming by this information from him.
Although it was a huge revelation in the source material, Netflix's The Umbrella Academy likely removed the link because it was related to a similarly excised plot point from the Dallas arc: the killing of JFK. Although there is a subplot in the show mentioning Hargreeves' involvement in the incident, it is much more prevalent in the comics, as Carmichael threatens to kill Luther and Five's mother as blackmail to drive the assassination. Without this kind of urgent danger relating to her, the revelation of the boys' mother would likely have only served to clutter the world of a season that already introduced a number of significant new characters, including Vanya's love interest Sissy, Allison's husband Raymond, and the mysterious Lila Pitts, in addition to making greater use of complex plot devices like time travel and alternate histories.
Of course, just because The Umbrella Academy hasn't yet mentioned Five and Luther's connection, that doesn't preclude the show from adding it in a future season. It's worth noting that Luther and Five were often paired up in season 2, establishing a dynamic that could be expanded upon and deepened later by giving them a literal fraternal bond. And although The Umbrella Academy does deviate from the comics' story fairly often, the introduction of Lila (a character unique to the Netflix series) and an alternate-timeline Sparrow Academy suggests that the show will explore the unusual nature of the 43 superpowered people in more detail than even the comics yet have, and a blood connection between Five and Luther would fit perfectly within such an exploration.