My autistic son hates his sister

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.

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.