Originally Posted by CM
I think that if Spin sees Yellow like a sister then it could explain why she is becoming protective of her. That and also I can see a tie in with the idea I sent you over PM (which I will not mention in detail here since it'd be a spoiler XP).
Elm's Pokemon are infinite, like Zubats. Whenever a new member joins they can still request a starter. It will just magically appear in Spinel's bag X3 But they will also receive a new trainers package with gives them an extra 20 points (I think that's a good number) and a common Pokemon that the team has already encountered.
Im going to add something in the story for you to get more. I had a good idea right now.