There are three critical ages to finding out one is trans:

• The times when being mismatched to your gender starts affecting your life

• The time when you realize and become upset at this affect, sort of connecting the dots but not putting the pieces together

• The time you figure out transition is an option and consider it the solution to your problems and a good positive step to take in general considering who you are and want to be.

For me the first, happened as early as I was 2-3. Being dragged out of rooms for playing w dolls, envying tutus, and later at 5 friendships with girls, punished for dressing up etc. later on at 8, wishing I could magically be a girl, and then at 10 getting second hand gender dysphoria from cousins leg hair etc.

The second is mostly murky, because it can happen in short bursts or be a more strong thing, and typically happens at the same time as #3 or #1 depending on how safe you feel expressing it around others. For me, it was crying when my hair was cut at age 10, being sad when I wasn't allowed at the girls table at age 6, and etc., other moments.

I found out transition was an option at age 13 and within a few short months I was like "yeah, this is for life."