The Umbrella Academy season 3 is sure to bring a lot of surprises, but one element that seems probably is that the story will contain two Fives. The end of season 2 already confirmed that the Sparrow Academy includes another iteration of Ben Hargreeves (number 6). Of the rest of the Umbrella Academy, Five is the other member that is most likely to have a cross-timeline doppelgänger.
The first two seasons of The Umbrella Academy followed the seven members of the eponymous group that was founded by Reginald Hargreeves. Relying on Five’s time travel as a key for the plot of both seasons, The Umbrella Academy season 2 already explored the idea of two Fives meeting. When the Umbrella Academy is transported back to the 1960s, the original Five tracks down the Five that is alive in this timeline, Older Five, to be able to steal his time travel briefcase. The interactions are relatively brief and see the characters plagued by the seven stages of paradox psychosis. When the group returns to the present day, the timeline has changed and Reginald Hargreeves now runs the Sparrow Academy and confirms Ben as a member of this new academy.
The Umbrella Academy season 2 showed Reginald Hargreeves meeting the six living members of the academy during their stint in the 1960s. This meeting was presumably the impetus that caused him to take a different path and start the Sparrow Academy instead. The only original member that Reginald, the Umbrella Academy’s father-figure, did not see was Ben as he was a ghost, which could be why he still recruited him for the new academy. During the meeting Reginald seems both a little scared of Five, and also extremely impressed. His understanding of the strength of Five’s power if used carefully makes Five the one member that he would be most likely to still try and recruit for the academy, which would result in two Fives playing major roles in season 3.
The members of the Sparrow Academy that are obscured from view in the final scenes of The Umbrella Academy season 2 remain a mystery. If Five is among them, he is likely to be portrayed by a different actor. His origin would have been very different in the Sparrow Academy: Reginald knew about Five’s power and how to guide him in its use from the beginning. Five would likely not have jumped forwards to the future, or back in time, and would have instead aged along with the rest of the academy.
It is possible that The Umbrella Academy season 3 will introduce doppelgängers for all of the original team, as they should still exist within this timeline. It is hard to say whether they would have learned to express their powers without Reginald’s teachings and they might think that they are normal people (Vanya went years without rediscovering her powers). Alternatively, they could have been recruited by another force as The Umbrella Academy season 2 showed with Lila and The Handler. However, it is also possible that Reginald would have killed the originals as infants. The end of season 2 showed how ruthless he can be and he has consistently been demonstrated to see human life transactionally.
While Reginald might have re-recruited Five into the Sparrow Academy, it is also possible that he is no longer part of that academy. His rebellious nature chafed against Reginald before and could do again, and his abilities might enable him to avoid any efforts to contain him. Ultimately, any doubles that appear in The Umbrella Academy season 3 will have to deal with paradox psychosis as previously established, leading them to have to split into separate teams if they wish to work together against the new Sparrow Academy.