Gallade and Gardevoir were owned by an Ace Trainer. The Trainer was fighting with Gardevoir in the Cafe, probably just not happy with Gardevoir's performance, causing Gardevoir to be sad. In a battle with Hilbert, both Gallade and Gardevoir get their shit beaten out of each other. The Trainer recalls them both, and the next thing he know, Gardevoir is gone. Either dead, traded away, sold, released or she just ran away. Whatever happened, Gardevoir is gone. Gallade, now angry, pushes the Trainer off a cliff, probably killing her.
Gothitelle and Prim, the Kirlia, see him doing this. He starts living with them, for reasons unknown. Gothitelle could've just mindraped him into thinking he needs to protect Prim, or maybe they knew each other, maybe they were the Trainer's other Pokemon, or maybe Prim was actually Gallade's daughter. Point is, they live together and care about each other to some extant. One day, Gallade sees Prim fucking a Golduck, and Gothitelle uses her magic to make him forget that, and creates an illusion of Gardevoir to live as Gallade's wife.
>>32067937Golduck didn't fuck her. She fucked Golduck. For the same reason she fucked the human. Heat.