Whilst I haven't had time to read through all the posts here, I can really identify with the mother and stepfather who started the thread.
Both myself and my partner are at the end of our tether with my 10 year old son.
My son's biological father was a very violent man, whom I left whilst I was pregnant, although I have had to put up with years of harrassment. I have had severe long term PTSD, with anxiety. He has never had any contact with his son (a court ruling prevents this). I had a relationship with someone for several years, who left quite suddenly (due to my the harrassment from my son's biological father) and did not explain to my son why. My son was 5 at this time, and could only remember this man being in his life. A couple of years later I met my partner, and we had a baby, who is now nearly 2. He also has 3 other children.
I know that my son was affected badly when my ex-partner left, and I understand that he has gone through a number of changes - including going from being an only child to one of 5. So when his behaviour started changing (before I met my partner, but got worse during my pregnancy during which I was very ill, my partner was away working most of the time, and I was and more inclined to ket things slide, particularly in the light of the changing circumstances) - not doing his schoolwork (he is now 2 years behind, but the school are not particularly concerned which is another HUGE issue), not looking after himself personal hygeine wise, occasional lying (to me) and taking things from within the house and hiding them in his room, refusing to eat what he is cooked yet taking food from the fridge when he has the opportunity - I disciplined him, but tried to understand at the same time. However, his behaviour has now got worse - and it is not only that these are isolated issues, there is a drip drip affect, which does result in such heightened stress...everything is a nightmare with him. He cannot be trusted, he never does as he is told, he won't keep himself clean in any way, and has 'breakdowns' (shouting, crying etc) if asked to shower or do his homework. He behaves most of the time as if he is 4 or 5, and cannot be trusted around the little ones. He lies constantly, and the final straw today was that he has taken money from us. Not much - £1. But he lied and lied about it - blatently. He never shows any remorse for anything, no shame nothing. The 2 older children, whilst only a year or two older, have no time for him now at all. He gets on better with children a couple of years younger than him. I dread him coming home, I dread the tension in the house, it is damaging the relationship with my partner - who, after all, is the father of my other child, and I do need to consider her too. The relationship between me and my son is bad, the relationship between my son and my partner is absolutely dreadful. His expectations of my son are no different from any of the others, yet it is consistently setting him up for a fall, as he seems incapable of following simple 'house rules' - which are for the safety and well being of everyone.
He is not violent - if anything, he is overly sensitive - grabbing him means you are trying to kill him. We have tried EVERYTHING - rewards, charts, withdrawal of rewards, punishment, time out, naughty step, tried to work with the school - who don't see a problem as he is OK at school apparently, apart from being behind. We did go to see someone professionally, but it was awful - we went before the behaviour stuff was too bad, when we were just concerned about his education, and the school were not doing anything (promises of special needs support, none materialising etc) but we were 'mis referred' ended up at child mental health where the person focussed solely on my background of a violent relationship and our stress, disregarded the other children, concluded he had low self esteem and that his school work didn't matter, we were over reacting. this was written in a report and based on a half hour 'chat' which involved me sobbing for most of the time as the person was dredging up past issues and questioning me on them. His behaviour got worse afterwards.
I could go on.
I won't, but the upshot is we are close to splitting up over it, and I know my partner hates him.