'Why is that? Children with ADHD can be responsible. My cousin has ADHD, he was also born addicted to heroine. He's a lovely child and wouldn't bully anyone.
Misunderstanding the nature of a disorder.
A disorder means that the children have common symptoms, not that they are the same, or even of the same aetiology: we know ds4 has a genetic anomaly, whereas I know another child also with ASD whose DX came from a brain infection.
Now, ds1- mini psychopath would probably describe him, we've been screaming for help for years; his fave passtime right now is killing insects, he gets 24 / 7 supervision right now but as he doesn't fit PIP system won;t as an adult. DS3 otoh is as far from a psychopath as can possibly be; sweet, friendly, caring. They have the same diagnosis, both correctly ascribed.
WRT to a child's understanding with ADHD- it's a very common saying and a true one that ASD and other spectrum disorders (of which ADHD is one) never stand alone, whether they are diagnosed or not. So likely the child had ASD, ODD, PDA as a co-morbid. Having worked with a child with a stand alone dx of adhd where nobody was interested in following the other clearly asd aspects of his personality once he ahd a label, it's quite common; as for surprise that the bully grew into an obnoxious adult- why? A child with AN is as likely to do that as anyone; indeed, being more susceptible to bullying more so? Am certain DS1's pathological symptomatology was not helped by severe bullying when he was in a MS environment! Of course I understand why those children responded to him as they did but they were not innocent as I now know- they have targeted innocent ds2 at comp level because if you daren't go for the bully, attacking his sibling seems to be the next best option.