In order to create new types of relationship between clients we will go to:
System --> Customers --> Relationships Types
We will open the following window, with the listing of all the types of kinship we have already created, from here we can create new types with the button 
, edit some of them with 
, or delete them 
.
To create a new one, click on the "New" button; the following window will open:
In this window we will insert the relationship type and its relationship inverse, that is in relation "Son", inverse relation "Father/Mother".