Well, he does demonstrate a lot of symptoms of something having happened to him in his past, over controlling, and wants everything to himself.
Due to this, he was probably an only child, left alone to himself, excluded by his peers. They probably had all sorts of battles without him, making sure to exclude him because of his condesending manner.
This may explain his hatred towards Pokemon and other humans, believing he's the only one who should have them.
Due to this personality, his first Pokemon may have been Dieno, because of its evolving into one of the most aggressive Pokemon out there and its being Dark, reflecting his own heart.
These are my views on his past.