I have to agree w/ Tina...the best form of discipline I have found (and I have researched TONS) is Parenting with Love and Logic... www.loveandlogic.com is the website.
It sounds like your son is looking for his "place" in the family and searching for attention, which is wonderful. Kids will get the attention they need in one way or another. If they can't get positive attention, then they will go for the negative attention. This is completely natural and you almost need to worry if it doesn't happen!
Being as tenacious as he is can be a good thing...if you handle it well now! The goal of Love and Logic is to teach your child how to think for himself, make and learn from bad decisions now, when the price tag is small. This creates adults that can actually function on their own and parents that can confidently allow their child to grow, knowing they have the ability to think for themselves.
When the negative behavior hits, you go Brain Dead...pick out a phrase and, very nicely, repeat it over and over. The key to this technique is to make sure you are locking in the empathy (Oh, how sad or What a bummer or Bless your heart), mean it and NEVER become angry and yelling. At that point, they have won. The child's goal is to see how far they can push before their parents say, No. Children really are in search of firm boundries. The trick is to lay them out in a manner that takes out the argument...or should I say, when YOU are not arguing...we all know you can't argue with a child w/o sounding like one! :-)
In our house, if one of my boys refuses to do something, I will say, "Oh, how sad." If that doesn't stop the behavior (which it didn't at first), then you go to the next step, which goes something like this...
Me: "Time to do your homework..."
Him: "I am not doing it now, I am eating a snack."
Me: "Oh, how sad..."
Him: "Mom...I said I am eating a snack" (even though he has been eating this snack for 30 minutes...)
Me: "I know, (pause for about 3 - 5 seconds) but what did I say..."
This is when the fun comes in...the first time I tried this, I was repeating this phrase for about an hour. I went about my normal schedule...loading the dishwasher, cooking dinner, folding laundry, etc. I heard things like, You can't make me do my homework (he was right...I can't physically make him do his homework), I am not going to do it...I don't care what you say, etc. After each statement, I just said, "I know, but what did I say?" My son got angry, I remained calm and even happily stated the phrase, in the same tone each time, and he finally stomped over to the table and said, "You are just lucky I am doing my homework because you can't make me do it." I just simply replied with "I know...thank you."
The other side of this coin is when is behaving correctly, praise him for it! Let him know that you appreciate and reward the positive behavior. Catch him doing something good, walk over and whisper in his ear, "It does my heart good to see you treat your brother so nicely". At first, you may have to search for ANYTHING to praise, but don't give up! As you continue, it will be easier!
Now, with my kids, if they hear the phrase, "Oh, how sad..." they know they have a problem that they have to solve. If I have to go to, "I know..." phrase, that is all it has taken in a very long time. My oldest will now tell me, "Mom...don't say it. I am getting it done!"
The funny thing is how well this technique (Love and Logic) works with adults as well!