In Sinnoh Folk Story 3, it says that humans and Pokémon used to get married. But what about Pokémon getting married to other Pokémon? Pic related. In the episode Snubbull Snobbery, this Snubbull almost gets married against her will to another Snubbull. The wedding doesn't happen only because Ash and the others happened to be there. Because of that episode, it is canon that there are Trainers who have their Pokémon get married to the Pokémon of other Trainers, potentially even if it's against the will of the Pokémon involved. Pretty messed up.