I have a Pathfinder character which is mostly an archer-type Ranger, but multiclassed with a level in sorcerer with the fey bloodline.
One aspect of the fey sorcerer bloodline, is the bloodline arcana "Whenever you cast a spell of the compulsion subschool, increase the spell's DC by +2."
Is it sensible that I interpret this as applying even when casting spells that aren't arcane spells (i.e. ranger spells)? I think so, it's not as if the text says "arcane spells" or such, but I thought it worth asking for second opinions.
(Keeping in theme, I also recently noticed the feat Fey Spell Versatility which could grant them access to some extra spells to use as as ranger spells (including a few options which they wouldn't normally have access to as either ranger or sorcerer). Even if one were to rule that the bloodline arcana didn't affect ranger spells normally, I kind of feel like it would be at least thematically appropriate to apply to ones compulsion subschool ones granted via this feat)