1- attribute "connector" 

The attribute "connector" is empty for family icons.
Couldn't we call the attribute some more generic name ("parent")?
It would allow to put :

• connector name if it is a connector icon
• family name for familly

2- html attributes spec

jmfrancois pointed that html attributes is a spec. you can do what ever data-* attributes, but connector is not defined here:
https://www.w3.org/TR/SVG/struct.html#SymbolElement

This mean that all non specified attributes shall be renamed in data-*