Sam's parents were in Team Rocket.
When he was a baby he climbed out of his crib and got into his father's experiments and viles and etc.
It modified his genetic code and added pokemon DNA. But pokemon evolve they don't grow into adults unless they evolve. So at the age he was at when turning into Latios they predicted he would die. So Team Rocket exploited it by saving a Rocket's son and gaining something out of it.
If he hadn't died or become a Latios... He would dangerously morph and change and grow pokemon traits, probably a specific pokemon's.
So Latios's DNA could match the cells imputed into him meaning they could turn him into the pokemon's DNA he had and a few others.
I was there to use him to defeat Team Volt and make sure he didn't get hurt.
Now Lettucecow you can make a backstory for yourself or we can.
But tell me so I can make one.
MY backstory is well mainly just I'm a powerful leader of the Rockets. I have the same amount of ranking and political power as the three Gym Leaders in the team but more power in pokemon and spirit etc.)
My other sigs I use: