I know how you feel, and sometimes it doesn't get better. My older brother has Aspergers, as do I, but he doesn't really have any empathy for people at all. He's about 41, still living off of the state despite having skills. Very lazy. Just wants to sit around and play secondlife.
I let him move in to my place because he needed to get out of his old room, it was filthy. Not a thing of his wasn't covered in mouse shit and urine. Had not cleaned in the five years he had the room. When he got here, my parents and I cleaned everything off for him.
Started doing weird and dangerous shit like leaving the oven or stove on all night, or leaving the water on. He's moved out, but I think he dropped a spoon or something in the sink. Need to fix it. I would ask him to clean (I work, go to school, have three pets to care for) and he's just sitting there playing games all damned day. he'd get in my face, scream at me at the top of his lungs. A grown ass man. Who is not 'that' disabled. We have the same disability. He was raised as a special snowflake where my parents catered to that behaviour, while I was raised to be disciplined. Neither parenting strategy was right, but the discipline and abuse made me want to to better. To get away. To be independent. So he would do things like push me down the stairs, scream at me if I even looked at him while he was in the kitchen. If I ate any of his food when I was running low (he would devour mine, I had to lock it up) I would ask him, "So you can eat my stuff, and I can't have this box of mac and cheese that's about 50 cents?" His answer is, "I'm not eating your food now, you're eating mine!" I ended up being very honest with him one day, I said, "You're a man child and you live like this because you don't have to put any effort into anything - you take advantage of everyone you know. All of our family members. You can do better but you don't because you're lazy. You need to move out."
Anyways, the point I am trying to make is that the kid needs his routines, but he shouldn't be allowed to get away with acting like that. He can control it. I did. My much more severely autistic friend did. It can be done. A therapist versed in the ways of autism will be able to guide them through the process. He might never understand empathy - in which case, is he acts out, have his parents take the minecraft away. He'll test them, for months. It will be hell. These are lessons that are better for him to learn while he is small and not my brother's age (and size) - throwing his sister down the stairs.
This may get downvoted, but unless you've been the sibling of an abusive goldenchild you won't understand what it's like to be abused and have no say in the matter. And be told there is nothing that can be done.
Not even the police would do anything. Family disowned me after I told him that he couldn't stay with me anymore. He manipulated the situation so badly, left out so many details of his wrongdoings, but has enough understanding not to act this way around my folks. They're his bread and butter. It's in insane dynamic to watch.
So yeah, give the two girls all the attention you can. They need it a lot more than he does. He really, really doesn't care for attention. Minecraft is his world, and unless he gets therapy while his brain is still mailable, then he may never learn to treat people properly.