We have had similar issues with DS5 at school. He likes to butt in then they are having their lessons with the teacher. He tells them their work is too easy. He is always blurting out the answers even when he isn't being asked for help.
I am curious to hear others advice as we haven't really found anything that is working yet. We have tried talking and explaining things to him.
I don't have any good advice on the sibling issues but I do have two younger children and I'm sure this will come up sooner or later.
