In the world of dreams the rules of reality do not necessarily apply. Each dream is unique and it's a direct link to the soul and spirit. Psychology provides its own theories on what dreams mean, but so did tradition and the study of dreams for thousands of years before any relevant science had developed.
Dream Meanings - Brother, sister
If you dream of your siblings then great joy awaits you. If you argue with your siblings then expect family problems that will make you feel bitter. If you are an only child but dream you have siblings then you will receive some unexpected help from someone.