So another thing.. for some reason I had always assumed you were limited to one familiar? But there is no restriction like that presented in the spell (although the grammar implies it).
I'd say that the existence in the "
Familiar's Law" spell list, a spell list specialised and dedicated to the management of familiars, of a "
Second familiar" and a "
Third familiar" spell in order to get more than one familiar strongly suggests one may only have one familiar…
That being said, indeed, nothing about the matter is explicitly written in the spell's description so it's up to GM to decide, IMO. As far as I'm concerned, I allow one familiar per such spell, meaning a character may have as many familiars as he actually knows (different) familiar spells.