Gru comes from a long lineage of Gru's. Although his hometown is unknown, in an interview with Ellen DeGeneres he claimed he was from Albuquerque, New Mexico. As a child he had always dreamed of going to the moon. He made a "prototype" rocket out of macaroni and an actual working prototype rocket. For most of his childhood he was neglected and ignored by his mother, and it is unknown if this is what inspired him to become a supervillain, or if the Gru family is a family of supervillains, although his mother showed no signs of being one. He has worked with Dr. Nefario, who builds gadgets and weapons for Gru, for some time and based on what Dr. Nefario said, they have been planning the moon heist for a long time.
At first, Gru was a sneaky and somewhat cold-hearted man, who was determined to become the greatest villain in the world. At first he showed a dislike of children being easily irritated by Agnes, Edith and Margo. He was selfish and in the beginning, he only adopted the girls so that he could get the shrink ray which he intended to use to shrink the moon so that he could steal it. He was also rather indifferent to their needs and welfare; when Edith was trapped inside an iron maiden and briefly presumed dead, he indifferently said that his plan could work with two children. Only that didn't work because Edith opened the door and said "It poked a hole in my juice box." Gru is also rather cruel and even sadistic at first and enjoyed using his Freeze Ray, which is his signature weapon often freezing people just for the sake of it. Near the beginning of the movie he made a balloon animal for a boy who'd dropped his ice cream and then popped the balloon just for fun. When Vector kidnapped his adopted daughters he furiously told him that he is in for a world of pain. However this is not a sign of his sadism; instead it is a sign of how much he cared for the three girls.Despite these traits, Gru is shown to be good friends with Dr. Nefario and also treated his Minions quite well interacting with them and calling each one of them by name (he can also understand their language) instead of just treating them like slaves. However he also said that he had no intention of giving his minions a raise. It is implied that Gru's negative personality traits stem primarily from his strained relationship with his mother, who was neglectful and somewhat verbally abusive towards him since his childhood despite his constant efforts to make her proud. As time went on, Gru started to enjoy spending time with his three adopted daughters and in the end he grew to genuinely love them, putting aside his dream of stealing the moon and risking his life to rescue them from Vector. Dr. Nefario disapproved of the fact that Gru's warmer side is starting to reveal itself and sent the girls back to the orphanage. Though Gru didn't attempt to stop Miss Hattie from taking them he is clearly upset about them leaving and later said that giving them up is the worst mistake he'd ever made. He also did his best to get to their dance performance after stealing the moon and is upset when he discovered he is too late. Gru also has a tendency to say "lightbulb" whenever he has an idea. He speaks in an unusual accent (probably east European) which was described as 'a mix of Ricardo Montalban and Bela Lugosi'. When asked about his accent by Ellen DeGeneres he said he was from Albuquerque, New Mexico and asked Ellen not to push this topic any further.