In the novel Thanos: Titan Consumed, we finally receive the full origin of Thanos. Born on the planet Titan in a place called the Eternal City, Thanos was the only son of A’Lars – The High Mentor of Titan and architect of the Eternal City. His mother Sui-San went crazy upon seeing him after birth and was removed from his life. Born with the deviant gene, Thanos was an outcast amongst his people. The color purple was specifically tied with death to the people of Titan. When someone on Titan died they were covered in purple shrouds.
Thanos grew at a fast rate. He had full mobility independent on assistance (walking correctly) at six months old and could talk full complex sentences with correct grammar by his first birthday. Due to his father and mother seemingly being disgusted by his appearance Thanos never truly wanted anything as a child except a feeling of belonging.
As a child he was a prodigy, reprogramming his father’s androids at four years old which caused his father to send him to school earlier than most. However, the school was not only too pedestrian for Thanos’ intellect but worrisome to children’s parents. Since he was lonely his father arranged for him to have a friend named Sintaa, although the kid was paid to hang out with Thanos for the next few years. Thanos soon learned of his mother being at a hospital yet not allowed to see Thanos.
When Thanos confronted a doctor about it, the situation escalated with Thanos killing the doctor with his fists. This brought Thanos his first true joy and felt right to him. However, it was later revealed the doctor was a synthetic life-form created by his father to watch his mother. By his twenties, Thanos was a genius in all scientific fields to the extent that he could manipulate living tissue at subcellular levels. His body was also more developed, with him seen as a genius mind stuck in the body of a brute.
The next time Thanos felt joy was when Sintaa took him to a club, and there he met a girl not afraid of his appearance. She gave him his first kiss. This brought a feeling of belonging he didn’t expect and made him think about his mother again. When his father was gone for a trip he made a surprise journey to visit The Mad Titan aka his mother. Although there was another synthetic droid blocking the way this time Thanos knew to outsmart the android’s programming instead of fighting it with his fights.
When he met his mother, her insanity and disgust for Thanos impacted him in many ways. One way was that he decided to help his society even though they hate him. He wanted them to see him not as a threat but as another member of society. When Thanos began looking at society to see how to help he came upon the conclusion that Titan was massively overpopulated. The overpopulation and its environmental impact on resources and germ breeding were projected to result in global pandemics, especially since they lived in a small location within The Eternal City.
Thanos presented his data to his father but when he didn’t take him seriously he presented it to the whole world, along with his idea of euthanizing half the population. This caused riots and suicides on Titan and people horrified at what Thanos presented exiled him from the planet. This was why he wasn’t present when Titan’s civilization finally collapsed as he predicted.