It's confusing to most parents at the beginning, more so before you've put it into action and seen some good results. Be sure and review the thread on adapting it to younger children at the top of this board because a lot is explained there.
On the surfact what it looks like at first is that you're giving into him most of the time. But what you really need to focus on is the long term goal--you're working toward helping to stabilize him, giving him time/space to relaz the knee jerk reaction to authority, and time to mature/develop skills to overcome his issues. It's critical that you look beyond the fact that the kid is getting his way most of the time.
At first it's recommended to start out with safety as basket A issues, then add on from there, and add on slowly (not 6 issues at once. As he is more settled he will more receptive to lessons that he can't get what he wants. By you taking a preventative approach you should see a big reduction in tantrums and hopefully eliminate the thought pattern of concern ("if I tantrum, I get my way").
Your ten year old daughter is old enough to understand that her brother has neurological issues that cause behavioral problems. What happened with my kids is that once they saw how much better our lives became when difficult child was stable, it really drove the message home and they were more understanding. They still don't like it all the time but in my opinion, that's just life--we don't live in a perfect world and a lot of life lessons grow out of hardship. I grew up with a special needs brother and didn't like it a lot of the time--in the long run there were many positive aspects I took with me into adulthood.
I have tried to ease the way somewhat for the siblings--ie when difficult child used to eat early because he HAD to to maintain his calm I didn't insist that they wait until suppertime. And I've eased up on expectations like keeping rooms neat and tidy because it's one of those things that really doesn't make a huge difference to me but not having the expectation helps them. I also made sure they all got one on one time with mom daily (usually bedtime) and that my oldest got special priveleges such as trips to the movies or bookstore when the younger ones were in bed. A child who is really
Do go ahead and read the other thread. You do really need to put it into practice to be able to see the benefits.