Michaela, please stop worrying. Breast lumps at your age are completely natural - as you say, your cousin has one, too. They're a sign of puberty; your breasts are growing. Please read our Teen Guide to Breast Development. It'll help you understand the changes you're going through, and that you'll cotinue to go through for several years.
It's good you're learning to be aware of changes in your breasts. As you get older, it's the best way to safeguard yourself against cancer. But at age 13 - well, the chances of you having breast cancer are way, WAY less than one in a million. So don't stress. But if you can't stop worrying - please tell your mom. She loves you, and she'll help you through this. Good luck - PJH
We hope you find this general health information helpful. Please note however, that this Q&A is meant to support not replace the professional medical advice you receive from your doctor. No information in the Answers above is intended to diagnose or treat any condition. The views expressed in the Answers above belong to the individuals who posted them and do not necessarily reflect the views of Remedy Health Media. Remedy Health Media does not review or edit content posted by our community members, but reserves the right to remove any material it deems inappropriate.