My middle boy is being a right pain in the proverbial, and I'm not sure if it's all because he's a threenager, or if some of it is more than that... I was wondering if I could tell you some of his behaviours, and you could let me know if any of your similar age children do anything like this...
1) won't talk to people when we're out and they speak to him. Just hides his face, or gives them evils. He's not shy, he just has days when he won't respond to anyone when we're out, even people he knows well.
2) Doesn't generally want to do much. For example I'll say 'Oh good, it's toddlers today' and he'll want to stay at home. Generally once we get somewhere he's fine, and will disappear confidently without me, but he just hates the idea of leaving the house. He's a total home bod and would just stay in and watch tv all day if he had the chance.
3) Refuses to do most of what I ask - including eating or trying anything new. Just flatly refuses. I try ignoring, praising the good, removing toys, naughty step etc - but he'll just not do it. Sometimes it results in a tantrum where he'll just repeat 'No, No' for hours on end. Usually at this point I remove him to his room for his own safety (so I don't end up clouting him) and then he'll scream and shout 'Mummy, no, please let me out' (the door isn't shut). I'll then say, 'OK - come down and say sorry' at which point he'll start again with the 'No, no's. This went on for 4 hours the other afternoon after he hit someone (he did fall asleep for an hour and a half, and then continued it afterwards). Honestly, sometimes I think he'll send me mad - and the neighbours will probably call social services thinking I've got him locked in a cupboard or something 
4) took him for school photo with his two brothers the other day. He totally refused to be in the picture, so I'll just have a lovely one of my 5 yr old and my baby instead. He generally hates being in group pics. Everyone will think I've only got 2 children from my albums..
So - is this just the usual - or is it more do you think? He's a very intelligent lovely boy a lot of the time, but other people are probably starting to think he's just a real pain. His speech is fantastic, he can count to twenty, knows a lot of letters and plays beautifully with his brothers. He's confident and funny, but this is being covered up by the other behaviour and it makes me sad..