W.S.
Tell me if you figure it out HA HA Actually, I don't have a complete cure but for playing nicely, I found it helped if I sent my dd to her room, ALONE, in a CALM and PLEASANT voice (not showing any displeasure or anger), saying she needed some "time out" and she could come out when she was ready to be nice to the others. The KEY is being calm (I found annoyance creeping in my voice and she'd react to that more unfavorably). At least, if it doesn't teach him right away, you've cut down on the squabbling for that time being.
With the whining it takes longer to "cure," but you have to make absolutely sure it NEVER pays off for him to whine. This is very hard to do, as it is easy when you are distracted or busy to just mouth off (negative attention can be just as reinforcing) or to give in. Whatever he is whining for, give him the EXACT OPPOSITE. For example, if he whines for another cookie, tell him "since you asked in a whiny voice instead of nice words, I am not going to give you another cookie--in fact, I'm taking the one you already have" or "you won't get a cookie for the rest of the day either" or whatever you think is appropriate. Again, delivered without showing your annoyance.
The key (not always easy) is to figure out what he is gaining by whining. He wouldn't keep doing it unless it somehow worked for him and he was getting SOMETHING out of it (even if it's just negative attention, or the feeling of power of seeing others get mad).
Again, it won't work right away, and may even get worse at first as he tests you, but if you stick with it and be consistent he WILL learn! (I know that's hard to do!)
Hope that helps!
Lynn