Hello and Thank you for responding. Your youngest son is saying all of the negative things and behaving badly because he is frustrated about the divorce, still having difficulty coping with the loss of his grandpa, and subconsciously in competition and probably always being compared to his brother. Those issues are very intense for a six year to process and handle. He is actually feeling a great deal of stress and anxiety because of the issues. There are a few routes that you can take. The first is to get your son into counseling. He needs to learn coping and intervention strategies in dealing with the issues that he is faced with through a process called Play Therapy. Also, you need to continue to pay special attention to your youngest son. Take only him on special outings. He is feeling neglected and you need to lift up his self esteem. Also, it may not be the best idea to have the brothers in the same class at school. Teachers often compare twins and it does have an effect on them.
Hope this provides you with some insight and direction. Have a great day!!!