Tags for navigating to siblings, with the reorder extension

Hi,

I am using the reorder extension with radiant, and I want each child
page to provide a navigation bar at the top to go to either the previous
child of the current page’s parent, or the next child. If the current
page is the first child, then there would be no previous link - and
similarly, the last child would have no active ‘next’ link.

This site is somewhat of an instruction manual where this kind of
navigation makes sense.

Thanks,

Ryan