negativity, disrespect, defiance

My son is 4years 9months old. He is very advanced for his age, always has been. He is very good at expressing himself, he spoke very early and by full sentences by age 1, he can read and overall he is ahead of his age deveopmentally. Until 3 he was an angel. Since three he transformed into a little menace. Also when he was 3 1/2 I got pregnant and now have an 8month old son. He never accepted his brother because he wanted a sister (he begged us to give him a sister since he was 2 1/2, was so happy when I was pregnant until we found out it was a boy).
We always tried to make the transition easier, spent one on one time with him, talked about his feelings etc. At first it seemed to be doing well but lately he is full of negativity. He is constanly questioning everything we tell him, he is rude, disrespectful and defiand. He is full of NOs and WHYs. We talk with him, ask him to tell us how he feels, why and if there is something bothering him. We tried enforcing good behaviour, rewarding repeated good behaviour, we try to set good examples, we talk and give opportunity to express his feelings. When all those failed we even tried time outs, depriving priviliges but still. It gets worse. We tell him something he immediately has the answer at the tip of his tongue.  
We don't know how to handle him any more. I have to add that he never was or is agressive or hurts physically. He does it with words.
Any suggestions will be very appreciated.
Thank you

[babygirl6152]

since he is so smart there are a few more things you can try-

when he thinks he has WON by not obeying, etc- let him think he has- then oh maybe an hour later when he asks for something special- and let's be clear I do not mean hugs or kisses or meals, anything like that but something SPECIAL- you could try saying-

remember when I asked you to pick up your toys before dinner and you screamed "NO" at me?
I would have preferred that  you picked up your toys when I asked you- I would have preferred you said "ok mom"- so let's try that again- you see where this is going- you are just retraining him to be a bit more cooperative- then it is up to you if you'd like to give him a fair exchange for obedience + respect = nice reward (cookie or whatever)-

I am so glad you are seeing how smart he is he can manipulate so early...And your getting ahold of it before he shows more opposition like physical defiance is wise. He is just testing you-  It will all work out..


hugs