In ShotGrid's "Version" player how to control which Versions constitute "Related Versions"

In ShotGrid’s “Version” player (i.e. the UI that pops up when you click a playable Version’s thumbnail", there is an option to see “Related Versions” as a right-side side bar by clicking the “Show Details” button in the upper left-hand corner.

What determines Versions are “Related Versions” to one particular Version, and is there a way to control what is and what is not “Related”?