Yes, yes, yes! That's a really cool thing to discover. I remember when I discovered it too. Then you get into inversions, and how *relative* minors really are "relative" to the initial key that they're in, e.g. in a C Major key with a chord of C-E-G, the relative minor is Am (move a third down from that and take away the top note for A-C-E); and you can mess around with blues progressions, and on and on. Isn't it fun?

Ellen