To find the relative minor of any major key, start on the 6th degree of the major scale. The following example shows the scale tone triads for the key of A minor, with the chords being derived from the natural minor scale. As you will see, the chords are exactly the same as those contained in the key of C major. The only difference is the starting and finishing point. Because the minor scale starts on A, A minor will now be chord I instead of VI.
The following progression could be described in two possible ways. It could be called VI I V VI IV V VI I V IV V VI in C major or I III VII I VI VII I III VII VI VII I in A minor. Because the progression has an obvious minor tonality, musicians would use the second description. Experiment with other chord combinations in the key of A minor.