Multiple familiars with a different progression

[frumple]

This one is giving me a headache.

I have a class that grants multiple familiars (similar to the pack master or broodlord archetypes for summoner but the familiar is of a single specific species). However, the familiars progress at a different rate than a standard familiar. (Basically, each familiar is 1/3 of a standard familiar in terms of HD and hp. The class gets a maximum of 3 familiars by 20th level)

I believe I am going to need to make a new familiar class in the vein of cArcFClass to make this work, but it looks like I cannot find the arcane familiar class in the editor to copy/inspect it to see how it works.

I could use some guidance on how to create this.