You can create as many Relationship Categories as you like.
Watch the walkthrough
https://www.loom.com/share/109268b80ca94e2489bb6af98ca7201e
Steps
Go to My Apps in the top menu
Select Contacts
Select the More Options button
Select Relationship Categories in the dropdown list
Select Create Relationship Category
Add in the two titles for each side of the Relationship, e.g. Father & Son
Press Save
You return to the Manage Relationship Categories page.
Now that the Relationship Category is created, you can use that Relationship to link two contacts together or to link a contact and a user