A major key and its relative minor share the same key signature but have different tonics (relative minor tonic = 6th degree of major)
Every major key has a relative minor key that uses exactly the same notes (same key signature) but treats a different note as the tonic. To find the relative minor: count 3 semitones (a minor third) down from the major tonic, or count up 6 scale degrees. To find the relative major: count 3 semitones up from the minor tonic. C major and A minor are relative pairs. This relationship is important for: key changes within songs, modal thinking, and understanding which chords are shared between relative pairs.
Examples
C major (0 sharps/flats) and A minor (0 sharps/flats) are relative pairs. The notes C D E F G A B appear in both; only the tonic changes.
Assessment
Find the relative minor of F major, D major, and Ab major. Find the relative major of B minor, C# minor, and G minor.