Many years ago, I figured out that my whiny toddler was not a terrible child. Like all of us, a child has a sin nature that needs to be curbed. That is not what I am talking about here. Many times that toddler was communicating the best way she knew. She needed a few minutes of her mom's attention. She did not know how to express that need. I don't know how to share that sometimes and I'm an adult! I noticed if I sat down and played or read a book to her then life got a lot better for both of us. She would run off an play by herself if I gave her a little time. I would have a chance to get my tasks around the house completed with out a small person hanging on my leg.
As a child grows, he may not hang on your leg but there is still a whine that occurs when he needs a parent's attention. It may be a little different than a toddlers whine but it is still a call for some attention. It may be some attention seeking behavior. If he's always punished for "bad behavior" then the call for mom or dad is lost.
A child who has a sibling(s) with special needs gives a lot. He does not get as much of mom and dad as he probably needs. Try giving your child(ren) without disabilities some special 1:1 time. She needs it. This will make both of your lives better in the long run.