idx = grandParent.childIndex(parent),
prev = idx - 1 > -1 ? grandParentChildren[idx-1] : null,
next = idx + 1 < grandParentChildren.length ? grandParentChildren[idx+1] : null;
idx = grandParent.childIndex(parent),
prev = idx - 1 > -1 ? grandParentChildren[idx-1] : null,
next = idx + 1 < grandParentChildren.length ? grandParentChildren[idx+1] : null;