I think it's just innate in some people. My second cousin was an only child and my aunt and uncle were great people, but he was already the neighbourhood bully as a toddler.
It stems from some external influence in their life. It doesn't have to be adults, it could be older siblings, cousins, family members, neighborhood children, etc. The effect could come from anywhere, but it just spreads like a nasty virus. I wish children had the need to spread LOVE and acceptance instead, but it doesn't always work that way.
iam sorry you asked a question? i couldnt hear it over the look of your avatar
People reap what they sow.