Family Issues Support Group
Family issues is a huge range that go from minor conflict to major misbehaviour and even abuse on the part of individual members of the family occur. Whether you feel you are in a dysfunctional family or you're dealing with a very specific issue, this is the place to talk about it and find others who might be going through the same thing.
I'm sorry that your brother acts unkindly towards your son. I hope that one day he realizes what a mistake he has made.
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Your parents are probably trying to make everyone play nice. Sometimes parents worry so much about keeping everyone happy that they don't realize that they are condoning sick behavior.
I would just accept that your brother is not someone you want to be with for your mental and physical health. If anyone asks you why you are staying away you can nicely say that you have nothing in common with him any more and he makes you uncomfortable. Remember we have no choice in our siblings but we do have a choice in how we deal with them.
I agree 100% with the advice others gave - stay away from him. At the least, he would be classified and having a borderline personality disorder. He could some day become psychotic. Now, I feel for those among us who have mental problems. The best thing for your brother would be to seek therapy ASAP before he hurts of kills someone. However, unless he has a compelling reason to seek help, he never will. It's sad. He is your brother, your sibling. But he is ill. You must stay away from him, keep your little boy from him, and let your parents handle it their way UNLESS you see them in physical danger from your brother. In that case, you would need to alert law enforcement.
I live in FL and it's filled with people who do not "fit in" in other places. This is not a good place for him to be, since he will likely prey on other unsuspecting people.
We always hurt the ones we love. But when someone acts out against someone who is not family, it's serious. Live your life, do not speak with your brother via phone other than to exchange necessary information, and stay safe.