What are some reasons why an only child would want a little brother or sister?

Many. As many answers as there are only children. It helps to ask them what they are thinking, focus less on the why or why not. As the single mom of an only teen son, I heard many different reasons depending upon the time of day! I was delighted to find out that he has a half brother and half sister. No need for me to have another child. Our blended families are learning how to co parent.