I grew up in a big family - 7 kids. Yours. Mine. Ours. I'm intimately familiar with sibling rivalries whether it was sports and competition, the seemingly endless pranks like short sheeting beds, or just the day-to-day stuff that drives each other crazy. I get it. However, I didn't have a sibling with a social and communication disorder.
The rivalries between my sons are not "normal" stuff like I mentioned above. They are rarely obvious and so filled with the complexities of autism that they make them difficult to identify and navigate through. The rivalries are really when his brothers push too hard, take too much charge of situations, or don't let games play out. M's best friend is his little brother. In some ways, though, the relationship is inverted as his little brother has been raised around therapists. He knows how to direct M. That's all fine and well until M has had enough. But they don't really compete in the traditional sense.
A sizable struggle throughout is that M's brothers don't know how to monitor where he is at, what's causing him issues and when he's had enough. Not that it's all on them to adopt but tracking M's status is an important skill to have if you want to connect withhim. From the outside when things go wrong it looks like M's emotional state goes from 0-60 in a second. Tracking that is hard enough for my wife and I. What comes out is a torrent of emotion. This is so polar opposite of his typical quite and kind behavior. It shocks my wife and I but really hits home on his siblings because his angst is pointed at them. Hurt feelings are exascerbated because he doesn't always have the right vocabulary to access so he uses words like "hate" and statements like "I wish I had a new family". Those things are tough to hear from a sibling especially when you don't see how you've hurt him. It's difficult to hear when you're 8 that talking too loud causes you're brother to hate you. That's not the same as bugging each other in the back seat of the station wagon or a fist fight with a sibling in your teens.
So my request to you is this. If you hear a parent like me talk about sibling issues when one is on the autism spectrum, please don't respond with blanket statements like "don't all siblings drive each other nuts once in awhile" or "that's just so normal". At some level I'd agree with you but what's different here is the fragility of the situation. What you think might be supporting comments may come off as dismissive. As a parent of a child with autism, I'm hyper senstive to dismissive comments because I've been fighting for his needs for so long. Instead, try a supporting statement like "that's got to be difficult to see happen" or "that must be tough for all of you guys". Those types of statements will make all difference.