[ Oh, now this is interesting. Well, it was time to play fast and loose(r) with the truth with this change in circumstances. No spoilers, after all.

He huffs in indignation. ]

Since the alternative would have cut everyone involved short in an incredibly bloody way. The team needed a spellcaster with experience in the arcane, not just a powerhouse like your dear brother.

Explaining anything else would stray too close to ignoring his surprisingly wise request.