Guardian (noun)

1. A person who has the legal responsibility for the care and control of a minor or someone who is unable to manage their own affairs.
2. A person who protects or defends something.

Origin:

Middle english: from old french gardien, from garder "keep, guard".

Examples:

1. He was appointed as the legal guardian of his sister.
2. She was the guardian of her younger brother.
3. The guardian was responsible for the welfare of the child.
4. The guardian was appointed by the court.
5. The guardian was the protector of the city.