Which Trinity Universe Characters belong with each developer?
I haven't played the game, but according to its English-language Wikipedia page:


Demon God Kanata
Valkyrie Rizelea
Fox Spirit Tsubaki
The Dark Hero Lucius
Treasure Hunter Recit
Managraphic Artist Miyu
Mizuki
Suzaku
Macaroon
Shuten
Ashura


are all original characters. 


Flonne
Etna
Prinny


are all Nippon Ichi characters from Disgaea: Hour of Darkness. (I can personally vouch for this one, since I've played Disgaea.)


Pamela Ibis
Violet Platane


are Gust characters from Atelier Viorate: Alchemist of Gramnad 2.