So. When Ash was 7 years old he had a little brother James. (Lol the name was based on my dream) When Ash was 7 years old he went to Professor Oak's Summer Camp (And Yes This Will Take Place on Kalos) So He's little brother James was left Not home but at a Pokémon Center where Delia told Nurse Joy to take care of him.
At the camp...
Ash was trying to find a Poliwag but instead he found an injured girl