Mother of a Transgender Person

Mac 🥀 • 🥀 Thought does not equal change. Change equals action. 🥀
(Hypothetical question)
You are the proud mother of an amazing young boy or girl. They are 13 years old. You notice that they start behaving the opposite gender role and remember that even when they were a little kid, they showed some signs of this, but you never thought much of it. One day, they come to you and say, "I'm transgender." 
1) What would be your initial reaction to this? 
2) Would you believe it's a phase?
3) How would you treat them from then on and would you respect their decision?
4) If they wished to go on hormones, would you allow it? Why or why not?
5) If they asked to get corrected surgery, would you approve of it? (When they're 18) Why or why not?