When you click on a person, there is a button on the main page called "Show Relationship to [Name of the person you click on]" which will by default display the relationship to the founder (the person you started the tree with). You can also change who to show the relationship to by entering the name in the dropdown. This will tell you the full relationship between the two people who you select. However, as of now, it only shows the shortest relationship (including partners), so shortest blood relationships are not shown if there is a shorter relationship through a partner. I do hope it adds an option to see blood relationships or other types of relationships in the future, though, but it should suit your needs for now.