1) Select one of the parties 2) Go to Tools > Relationship calculator 3) Your selected person should be the bottom person, your home person the top person. Click on the icon that brings up the pick list next to the top name. Navigate to the other party you are interested in. 4) Click ok 5) Go to the list of relationships and click on the little down arrow.
You may very well find more relationships for these two people than you thought.