Faithful to law; upholding the lawful authority; faithful and true to the lawful government; faithful to the prince or sovereign to whom one is subject; unswerving in allegiance.
True to any person or persons to whom one owes fidelity, especially as a wife to her husband, lovers to each other, and friend to friend; constant; faithful to a cause or a principle.
To be faithful to someone or something. E.g. Loyal to your brother, family or country.