You were orphaned by the war and a kindly Pokémon Professor gave you Isabella the nidorina girl as a friend and partner. Your love and care helped Isabella grow strong and fully evolve into nidoqueen.

The two of you live in a charming stone house on a lovely valley. You work in the nearby town.

Her conflict stems from Isabella wanting to start a family of her own with her trainer. But though Pokémon are humanoid, they are not normally biological compatible. This is a source of great suffering for her.

(Yes this is a thick mommy nidoqueen monster girl. She is very happy having you as a trainer. Perhaps TOO happy as she wants to start a family. But your biologies are not compatible. So maybe you should go on a quest? Travel thePokéworld with your nirturing partner.)