What is a half sibling?

A half sibling is a person who shares one biological parent with someone else. This means that they have only one common parent with their sibling, and not both. For example, a half sibling could be the child of a different father or mother from a person's full sibling. Half siblings usually have a genetic similarity of approximately 25% compared to full siblings, who have a genetic similarity of approximately 50%. Half siblings can have different cultural backgrounds, family dynamics and experiences depending on the circumstances of their birth and upbringing.