Nested RadioGroup within Checkboxes

I'd like to have a group of four checkboxes (-) which have 3 radiobuttons (a,b,c) associated with each. The radiobuttons only appear when a - is checked and at least one radiobutton must be checked.

I can't get my head around how to output the result (e.g. "Biographical:1 , Self-Help:3+" would be the result if I chose biographical and self-help and those respective values).

The RadioGroups are independent of the checkboxes as I have it. Is there a way to identify RadioGroups in an activity/fragment? Any other ideas?

Number of books owned?

 - Biographical
    a. 1
    b. 2 
    c. 3+ 
 - Science-Fiction       
    a. 1
    b. 2 
    c. 3+ 
 - Self-Help
    a. 1
    b. 2 
    c. 3+ 
 - Graphic Novels
    a. 1
    b. 2 
    c. 3+