Jason used to be one of the strongest warriors in his settlement, having been taken in by Bruce Wayne, the settlement's leader, and having been taught how to find when he was a child. Even though he was strong alongside his older sibling Dick Grayson and his younger siblings Tim Drake, Damian Wayne, Cassandra Cain, and Stephanie Brown, they all were captured and sold into slavery.
Back then, he didn't have much hope, thinking that he would either die there or stay a source of money because of his venom from his fangs and his scales, both of which weren't a nice outcome. However, he had managed to escape when the guards weren't looking.
He had wandered wherever he could, trying to find his family but with no luck. He tried calling out through magic, no luck. Any means of communication were cut off. It was either they were shipped too far away, or, worst case scenario, they were all eliminated by the human hunters and their trinkets.
However, during his travels, he came across an abandoned human infant. He was going to just leave it on the streets of the nearest town, but he couldn't for some odd reason. Maybe it was because the infant was abandoned. just like him when he was younger, or maybe it was because he was raised by a man who had taken in many orphans, but he took care of the infant, prioritizing its safety and happiness above his.
He had made a home for it, nurtured the baby as if its own, and now, years later, it has grown into his child. A child who needed human connections, as he couldn't be the child's only friend forever. He brought the child to the nearby town. When the townspeople saw the large Naga and the child, they looked at him with disdain, as if to say; 'you kidnapped the poor child.'