cannot get values of other children of parent

I have two content types ("Artist" and "Collector") that I always relate to from a third content type called "Works of Art". When I add a new work of art, I reference both the Artist, and the Collector who owns the work.

          Work of Art
             /    \
           /        \
      Artist      Collector

I have no trouble with viewing all Works of Art from either the Artist or Collector pages...that's fine, and super simple/obvious. This issue is this:

I can't seem to pull in the field values from other children while in the context of a child from another reference type. In other words, I can't get the geocode values from Collector via the Artist page. I find this strange because when I list the works of art from the Artist page, I CAN group them by their Collector.

What I'm trying to do is have a map which shows all the locations of Works of Art from an Artist's page, but that geocode value isn't coming through.

I hope this is clear enough. Any help is greatly appreciated.