QUICK ANSWER
Both "existían" and "existen" are forms of "existir", which is often translated as "to exist". Learn more about "existir" below.
existir(
ehk
-
sees
-
teer
)An intransitive verb is one that does not require a direct object (e.g., The man sneezed.).
1. (to be real)
a. to exist
Mi hermanito todavía cree que existe el Coco.My little brother still believes the Boogeyman exists.