I know that you can find files that have X number of links.
From the Manpage. Use these with the find command.
-links n (some number of links)
-linkedto path
True if the file is the same physical file as the file specified by path (i.e., linked to path). This primary is similar to -inum, but correctly detects when a file is hard-linked to path, even when multiple file systems are searched.
I thought that I had heard of a way to find the links to a file, but I can't remember right now.