No, William and Harry do not have a biological sister.
While Princes William and Harry do not have a biological sister, they do have a step-sister and step-brother through their father, King Charles III's, marriage to Camilla Parker Bowles.
William and Harry's Step-Siblings
| Relationship | Name | Details |
|---|---|---|
| Step-Sister | Laura Lopes | Daughter of Camilla Parker Bowles from her previous marriage to Andrew Parker Bowles. She generally avoids the public eye. |
| Step-Brother | Tom Parker Bowles | Son of Camilla Parker Bowles from her previous marriage to Andrew Parker Bowles. |
Although Laura Lopes is not often in the public eye, she is a known part of the family and has been since Charles and Camilla married. This step-sibling relationship is acknowledged in the royal family.
