My autistic son hates his sister

I’m so sorry you had to go through this. How could your parents have done better? I’m worried about the impact of my elder son’s ASD on his younger brother, who just adores him, but is constantly rejected by his big bro.

Having grown up with an autistic sister who would not touch anything of hers that I touched and repeatedly treated me as though she hates me, please be aware of the impact this will have on the non-autistic sibling. For example it left me with feelings of unworthiness, low self esteem as if there was something wrong with me. I was constantly blamed as everyone wanted to avoid a meltdown from my sister. But touching someone else's belongings is not a crime and was certainly not done on purpose as a poster here suggests- the non- autistic sibling should not be blamed. . This has led to a life time of people pleasing, ignoring my own needs in relationships, interpreting really negative behaviour as "love" because that's what I was told my sister felt for me whereas there is zero evidence of this even now we are in our 50s. 

She still will hate everything I profess to like as a matter of principle, acts revolted if I cook for her, never asks me a question about myself and I'm tired of it. I know logically she cannot help it...or can she? At what point is a label license to act in unacceptable ways? Back then my parents didnt have strategies, support or even a diagnosis to help them - I just had to be the "good girl" and not do anything that would be deemed annoying in any way to my sister and those "things" were just regular things. This has continued with how she treats my daughter ( but not my son interestingly enough... although she didnt even so much as text when he had cancer until forced to by my mother) My daughter said at age 6 "Why does my Auntie hate me?"

My mother forces us into family occasions which are not enjoyable for any of us. My sister is visibly stressed. I have self harmed prior to having to go through with them. Whilst I can sympathise with the challenges of being autistic, the impact is felt by everyone. Think about how the child who is told her voice is intolerable to her sibling- as someone suggests below -feels ? Where is she allowed to use her voice? How might it impact on how she speaks in the classroom or in social situations? Why are her needs to speak/be heard secondary? 

I have not even scratched the surface of making sense of my experiences but I do appreciate finding posts here that reflect my childhood experiences 

At that age, is there a chance she might secretly enjoy his annoyance? This can make her feel a bit of "power over" which he might sense and further loathe, as Autistics can often sense motives or an underlying system at play, but not always be able to call them out due to difficulty with vocabulary or assigning the name to the item/ manoeuvre/ intent and so on (which compounds the frustration).

Sibling 'rivalry' at this age is typical for any house. Due to autistics being - often - far more intensely impacted by internal and external sense perception (emotionally, psychologically, and then our senses like smell & hearing), this will be a bit more intense I'm afraid.

I'm curious as to why she touched his swimming costume. Sometimes it's the child with more power who needs help learning to use it responsibly. Even ignoring is a tactic which can wield a psychological thrill. And these things aren't any different for any child, really. We can learn a great deal about ourselves in relationship with our siblings. 

It can be difficult at that age for autistic and non-autistic children to get along, depending on their personality. They may simply irritate each other. It could be much harder to help him express what he doesn't trust about her or what simply irritates him. But it might be good to begin to sit them down once a week and pick one thing to sort. Start a list with each, maybe a notebook and allow them to be brutally honest. Is your daughter embarrassed by him? Does your son feel her presence robs his identity? A therapist might encourage speaking the worst of the worst. Raw unrestrained confession is often the gateway to reconciliation/healing.

NAS24917 said:

Avoiding his sister is his 100 per cent occupation.

With the avoidance it sounds as if it could be anxiety based. 

Has he been able to communicate why he reacts the way he does?

NAS24917 said:

He screeches if She appears in his sight, even if she is completely silent.

One possibility is that it is sensory anxiety if he can't tolerate the sound of his sister's voice. He won't want to go near anything or anyone that might potentially make a noise he finds intolerable. I'm like that with certain dogs. If that is a factor then ear protection might help to a certain extent.

Does he have something he is interested in that he would strongly want to participate in? Maybe if you could set up such an activity and include his sister. Warn him in advance that his sister will be there and give him the autonomy to choose if he wants to join in or not based on that knowledge.

If nothing else that will test if his aversion to his sister is greater than his interests, so you can begin to understand what you are dealing with.