MARÍA POSADA, MANOLO SÁNCHEZ, and JOAQUÍN MONDRAGON from THE BOOK OF LIFE
Justification:
"The three are childhood friends and the two boys always joked and playfully fought about María marrying one of them… Then the gods of Death made a bet on who María would end up with. Seriously.
La Muerte (queen of Land of The Remembered) bet on Manolo and Xibalba (king of Land of The Forgotten) bet on Joaquín, and if Xibalba won, they would switch places. Xibalba gave Joaquín a MacGuffin for him to not die, and killed Manolo (he came back tho and kicked Xibalba's ass).
Polyamory would've quite literally saved Manolo. Also, they're such a cool battle throuple!
(also I had to search some of the names and found out they're making a sequel and I'M SOO HYPED NOW!!!)" - @octonine