In The Umbrella Academy Season 1, we learned that Ben Hargreeves died and Klaus was his only gateway for posthumous communication. Season 2 pushed the envelope a bit, implying the circumstances of Ben’s untimely demise without outright confirming them. However, it’s possible that Season 3 will finally reveal the truth. Actor Justin Min recently threw his support behind a popular fan theory about what happened to his character.
Spoilers ahead for The Umbrella Academy Season 2.
Following his death, Ben chose to stay behind rather than go into the light. He’s stuck with Klaus ever since. In a Season 2 flashback, the Hargreeves siblings were seen attending Ben’s funeral and getting a stern lecture from their (alien) father Reginald. They were obviously torn up about their brother’s death and their discussion indicated that he died during a mission gone wrong. That’s the extent of what we know so far.