How are transgenders identified at birth?
Answers
The individual identifies that they're transgender because they fundamentally disagree with the gender that they were assigned by the doctors and their parents at birth. That is the point at which someone who is transgender can begin taking steps to address the gender identity by transitioning socially (by changing their name, appearance, pronouns, etc.), medically (beginning Hormone Replacement Therapy, undertaking Gender Reassignment Surgery, etc.), or both.
This can happen during childhood, as a teenager, during adulthood, or even as a senior citizen… many people know it when they're young and repress the feelings because they're ashamed or afraid, which is why many people begin their transitions later in life. This is also why you see instances of “hyper-masculinity” in trans women or femininity in trans men. It's an attempt (either on their own or imposed by family or society) to repress their identity and “just man up.”