Sir Reginald Hargreeves adopted seven of the forty-three children who were all born on the same day in 1989 to mothers without any previous signs of pregnancy. He intended to train the children to save the world. Sir Reginald is played by Colm Feore in the Netflix adaptation of The Umbrella Academy.
Sir Reginald came from a time long ago devasted by nuclear war. He traveled to the 19th century and founded a business that specializes in producing umbrellas, which is how he made his fortune as a billionaire for a hundred years. On the night of 1989, when forty-three women gave birth to children with unique feats and abilities, he adopts seven of the children and founded the Umbrella Academy in hopes of training a team of superheroes to prevent another apocalyptic scenario that would befall the world, which he had predicted to occur sometime after the Umbrella Academy broke up. He had orchestrated his own suicide to reunite his adopted children to bring back the Umbrella Academy in order to prevent the end times.
Hargreeves was an incredibly complicated individual. He was cold, distant and emotionally abusive towards his "children", treating them more like lab rats than humans. He never gave them real names, only referring to them as numbers he assigned in order of how useful he viewed them. He blatantly played favorites, called Vanya useless, and locked Klaus in a mausoleum in order to test his powers.
His treatment of the Umbrella Academy is the cause of their dysfunctional relationships, multiple neuroses and destructive behavior.
At the same time he showed moments of deep concern for his children, he gave Vanya her violin, despite it being a memento of great importance to him. He also expressed sincere guilt and concern about Luther's well being while talking with Klaus in the after life.
In Episode 10 of Season 1, he is seen with a woman who is either his lover or wife who is visibly sick. She is not named but she calls him 'Reg' and tells him to leave her to die, as the world 'needs him'. Sir Reginald does as asked but never speaks of her again.