Hello, and thanks for your question.
The expert you requested doesn't seem to be available since you asked your question, yesterday, so I would like to help.
My name is ***** ***** the situation you describe with your son and his older sister, sounds like bullying. You need to have a serious talk with your daughter about what she is doing to her brother, and if he says he feels like an elephant is sitting on his chest, he IS being hurt, physically, and this is no laughing matter.
Your daughter and her friends should not be permitted to take advantage of your son in this way and if the behavior does not stop after you speak with your daughter and set the boundaries, you will need to take privileges away from her as a punishment.
In addition, tell your daughter that her water polo friends are no longer welcome in your home, because of what they did to her brother. I have a feeling, they did this at her suggestion, but they should know better, being older.
Your daughter is trying to wield her power (physically and emotionally) over her younger brother and this is not right, nor is it good for his self-esteem. It can cause major problems as he grows older and make him feel a lack of confidence. Your son is at a very significant age, now, being a new 'teen' and for boys it is a very uncertain time, with hormones raging and self-esteem issues, even if this particular problem wasn't taking place.
You should supervise your children's time together, to make sure this doesn't happen anymore and if you can't supervise, separate them into their respective rooms. Your daughter shouldn't be allowed to bring any friends over, when you're not home, in the future.
This is pure torture for your son, and you need to stop this behavior, immediately.
I hope things improve, very soon!
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