In this article in Scientific American , it says some children insist, from the moment they can speak, that they are not the gender indicated by their biological sex. In which case, it there a possibility that this knowledge lies in a biological component?
According to various studies, there is a likelihood that there is a biological basis for gender dysphoria. But it will be a long time before a doctor can do a brain scan on a child and say, “Yes, this child is trans.” Until then, one can only continue research and attempt to be as trans-inclusive as possible. For details on the studies, read the article.