M.H.
Perhaps a social story will help your kids to better understand how to deal with one another. A social story is a tool that is to teach kids very specific patterns of behavior and acceptable responses. The story could be called, "Sharing and Caring in Our Family".
All you do is write very obvious, simple statements on each page and then draw a very simple picture, such as a happy or sad face or a picture of a crayon and two smiling faces - describe the problem behavior, describe the way other people feel when that behavior happens, then describe the proper behavior and how people feel when that happens. Always use positive, descriptive language to describe the behaviors - do not say one is bad - just do a good job showing the consequence of the unacceptable behavior so the child understands that it is the behavior that is causing another to be sad - not the child himself.
I hope helps. It has made our home life much much happier!!!! My kids ask to write these stories now - and we do it together with them describing feelings, pictures, etc. Good luck and Blessings to you and yours!!!!
A great book that helped with this process: http://www.amazon.com/gp/product/188547766X/ref=oss_product