How to navigate the maze of behavioural disorders

As a newborn, Rayan ticked all the boxes—the pregnancy was without any complications and he was a full-term baby with appropriate weight. He was in our daycare since he was eight months old. While he reached most of his physical milestones such as crawling, sitting, standing and walking, he preferred to be alone and never mixed with other children of his age. By the time he turned two, he had never responded to his name. He had never spoken a single word, only pointing to things he wanted. He also engaged only in solitary activities. 

Then there was Kartik, one …