Sorry, anon, that is not correct. Ignoring removes for now, when the common ancestor is a grandparent, that's a first cousin. One G. Your first cousin's children are your children's second cousins. Those children's common ancestor is your grandparent, their great grandparent. Two Gs, second cousins. Confirm with the chart. As you describe it, there is no name for the relationship when the common ancestor is a great grandparent.