If you're talking about the phenomenon of a Servant double summon, for the sake of consistency since lore can get confusing at times, imma put a hard pass on that.
As for the Persona one, hmm... @Thepotatogod imma leave this one to you since you're an expert on it.
Amelia Wilford & Miku Nanairo
Tamamo attempted to block Sett's fist, only for the kinetic energy to push her back. When she got up, she had quickly noticed Zenitsu who jumped high enough to deliver an overhead slash. She spun around and then threw a kick to the midsection right before the blade...