The Quest for the Legends

Alan: We took all of them, but only kept her. The rest we took to a nearby adoption center.

May: Great. A Blaziken now.

Alan: How did I evolve them? They just… evolved. o-O That's a weird question. And Mist doesn't know what happened to her siblings after we gave them up to that adoption center.

Tyranitar: …

May: I figure he can talk, but just doesn't like talking.

Alan: Huh? No, I'd have taken her siblings in too if they'd still been there, but they'd all wandered off by then and we couldn't find then.

Charizard: Well, I talk a lot to Dragonite, so I suppose it would be him.

Gyarados: Terrible, but I was hungry.

Letaligon: I do not know why I am different from all the others. I should have been shiny but wasn't.

After my father is dead, I will go off on my own and find a different herd to join.

Mark: Huh? Games? I mean, there are some virtual Pokémon battle simulators, but nothing more than that.

Letaligon: I have no interest in killing all the shiny Letaligon. I will kill my father, and I will watch my siblings kill one another. And then I will go and find another herd to live with.

Edit: I just read Alan's pokemon bios, and I must, say congratulations! You made three completly different backstorys for Mist in the ILCOE!

Three? What are you talking about? This one is the original one. I got confused at one point here in Ask the Characters and made up some deal with an adoption center, but that has already been made uncanonical, and the only other one has been exactly this one as far as I can tell. Even then, the only difference is in what happened to Mist's siblings, which technically does not change her backstory at all; she has consistently been found in a cardboard box in Itsruban, always having wanted to evolve into a Vaporeon.