The signs that you have a trans child on your hands show up as early as age 3 in some cases. With more parent opting to let their kids transition earlier or determine their gender identity, the need for support serives and organizations for trans youth and their parents has grown exponentially over the last decade.
If you are looking for some sites and organizations who provide information and support for the parents and loved ones of a trans child, here are some links. This will be a ongoing project
Trans Youth Family Allies
Trans Kids Purple Rainbow Foundation
Camp Aranu'tiq