It was unknown to Professor Oak that on the same day his Grandson, Gary, turned three he would also find a baby wrapped in a Team Rocket uniform on his door step.
He looked around for someone but didn't see anyone and it was starting to rain. So he took the baby inside and got it wrapped in a proper blanket and made it comfortable while he hide the uniform.
This boy was going to someday ask about his parents and this uniform is all he had to tell anything about the parents and it wasn't good. This kid didn't need to know his parents are criminals he just needs to grow up and love Pokemon.
That is exactly what Professor Oak did. The young lad grew up along side Ash Ketchum, Gary Oak and the other kids of Pallet Town. Yet he still seemed to be a social outcast and would rather read books then play games and pretend to be a Pokémon trainer.
All he really knew of his parents was what he was always told and that was that they died shortly after he was born.
Professor Oak became like a father to him and taught him about Pokemon, but he was more interested in Pokeballs and how they worked, which made him different.
The only friend he had growing was a little Pikachu who didn't like his Pokeball no matter what changes the lad made to it. The lad and Pikachu grew very close together and he became the first person the pokemon trusted which was really saying something.
The lad by the way is none other then the Famous Pokeball Professor, Foxx!