They make you laugh, drive you mad and will be your friend for life.
Brothers and Sisters are among the most important people in the world to us.
We wanted to find out what you think so asked a group of more than 1000 children aged 7-12 to tell us all about their experiences.
Whether you're the oldest, youngest, middle or an only child you had a lot to say about what it's like being in your family.
Here's some of the results from the survey by Childwise.