Constituent relationships are a setting and not a code table. 

To add relationships
  1. Go to Constituent Relationship settings (under Configuration)
  2. Click Relationship types for individual constituent records, or Corporate Relationships for organization relationships to constituents. 
  3. Click Add
To edit existing relationships
  1. Go to Constituent Relationship settings (under Configuration)
  2. Click Relationship types for individual constituent records, or Corporate Relationships for organization relationships to constituents. 
  3. Find your relationship pairing and hit the dropdown arrows
  4. Click Edit