Maybe Vertega and Eugene are just inhabiting the same body, and can switch back and forth at will. Eugene’s just letting Vertega have his fun cuz Eugene’s the first person in history to sympathize with Vertega
Eugene is now Vertega’s real family; and neither will die (as in exit the reincarnation cycle) or leave each other like the cartel did for vertega
I dont think Vertega is necessarily on their side, I think all his previous grudges have been slightly mitigated due to Eugene, so he’s just working for his own desires. Which may or may not align with Eugene/Levant/friends’ goals.