my boys are 3 and 6 so they aren't exactly the same age but I'm working through the same conflicts.
The first thing to do is lay down the rules. No hitting, kicking, biting, spitting. List all the mean things they do.
No talking back to mom.
Follow instructions the first time.
Then you tell them you will give them a choice between following the rule or they will lose something. Start with their favorite things then work your way down to losing their freedom. Yes that means you may have to strip their rooms of everything including decor then leave them there. You tell them up front, that they will choose or you will enfore the negative choice and that will cost them something
You say, "Johnny you have a choice get out of your brother's personal space right now or you can lose your television privileges for the night. " Then follow through. To get something back they have to be good for an hour for every year of age. To request it back they need to come to you and apologize for whatever they did wrong and ask for a hug. you can say, "First you need to say I'm sorry mommy for hitting my brother with that pillow" then you can say "Okay, now can I have a hug" they need to hug and apologize to each other as well.
You husband has to be in on this, he has to practice it when he's at home.
Here's a place to go to get more information on choices and the motivations behind bad behavior. http://lifematters.com/step.asp
Once you have the new rules posted and understood you need to make an extra effort to share something fun with each of the kids alone.
Here's what we do. The younger one gets into the bath at 8. His bath time is over after only 5 minutes then I sit down for special time for 5 minutes then we read for 20 minutes and he goes to bed. Then I start the older one's bedtime routine.
The older one is on the computer (subject to having compeuter priviledges at the time) while I'm working with the younger one.
Special time is something that you do totally alone with one kid at a time. You bring out 2 toys that don't have rules put them at a table and say "this is our special time you can choose from one of these toys to play with me." once he chooses then you put the other one away and sit down at the table, Then you tell him that you two can play at the table but if he gets up you can't play with him. (keep in mind that if he gets lippy, or aggressive with his speech toward you the time is over and you tell him so and that you are putting the stuff away right then, but you are still going to read---no exceptions. And this time is not contingent on good behavior outside of special time.)
Here are the rules you must follow during special time
No questions
No commands
No conflicting statements like "well we do things this way"
then you focus on these things:
*Praise him for every thing. I like it when you choose the green blocks, I loved the way you stacked those legos, I am happy that you are smiling. I appreciated you picking that toy up off the floor.
*Reflection: if he says something nice you repeat it
*Imitation: if he chooses a yellow block you choose a yellow block too
*Description: You chose a yellow block, you placed that leggo on the top, on the table... eventually you can spin them into praise too. You chose to put that yellow block on top of the tower. You had a great idea to put that block on top of the tower.
Enthusiasm: act excited at every good move and word.
At the end of the 5 minutes you tell him special time is over and you are going to put away the toys, he doesn't have to help but you are going to put away the toys.
Then you move on to books.
This really lets them know that good words can come from you. So during the day use those praises. You have to go beyond, good job, and Thank you to saying "Johnny, you did a good job picking up the cereal that was spilled on the floor!!!!" even if he spilled it and you had to tell him to clean it up after punishing him.
the motive is to say 100X more good things than bad and it can really feel fake at first but when it becomes a natural part of you the kids will act better.
You did a wonderful thing looking for other options on the internet.