Actually, though they look quite similar, they are separate breeds, and are just as related to other breeds as to each other. They are both herding breeds, but I disagree that Collies are nippier than Shelties, I have found quite the opposite to be true! And the Shelties I have known personally had more than enough attitude for any size dog! They both can be "nippy" but that is part of their job as herding breeds - nip the sheep to keep them heading in the right direction!