Alright, this is my first so bear with me if this doesn't work.
I've been around since the start,
It is said that I control my kinds evolution,
under the ceremonial full moon,
Although I didn't bloom with Ash,
I flourished before Dawn
Nope, look at the last two sentences, note the both Ash and Dawn, the characters are noted in the riddle. The riddles answer is linked to one of Ash's Pokemon.