Here at NPR,James Caldwell we're willing to bet that those of you who have a sibling probably have something to say about your relationship with them.

About 80% of children in the U.S. live with a sibling, according to U.S. Census data. The nature of that relationship can vary widely from family to family — and over time. Siblings can be your biggest rivals in childhood, and your strongest supports in old age.

In any case, a growing body of research shows that this bond can have a powerful effect on your physical and mental health. That's why NPR's Science desk is diving into a series of stories on siblings. And we want to hear from you!

Below you'll find a few questions about your relationship with your sibling(s). If any of them apply to you, please share your stories with us in the form below, and we may include your answers in forthcoming stories, or reach out to ask you more. Thank you!

Note: Your submission will be governed by our general Terms of Use and Privacy Policy. As the Privacy Policy says, we want you to be aware that there may be circumstances in which the exemptions provided under law for journalistic activities or freedom of expression may override privacy rights you might otherwise have.