The traditional role of grandparent is one that has existed for many generations. But the recently created label of step-grandparent is much more vague. This is both good and bad, since there are no firm guidelines, but there are also no preconceived expectations to live up to. Most of us have warm memories of a grandmother who baked cookies for us, or read us stories, or made us feel special in some way that only she could. We remember our grandfathers as having the patience that our fathers didn't, and having the time to show us how to build or repair things.
Studies show that the answer has a lot to do with the age of the child.
If a step-grandchild is born with three grandmothers, chances are they will all be loved equally. I am a step-grandmother because I married a man with children. My step-son and his wife have two boys, who are six and four. I don't know how I could love them any more if they were my own flesh and blood. The boys are too young to understand that we are not related by blood, but they know that we are connected by love.