"Some of it's more obvious with certain theories. Emotions, brain chemistry. Siblings and blood relations, the closer the better. Poignancy. Romantic relationships. Best life-long friends. Sure, there's an issue of not having the resources to make enough jaegers for everyone, but not everyone seems to be drift compatible. Or at least, not with who they think they should be."

He's quiet for a few moments before nudging York with an elbow. "I'm thinking too hard about it, aren't I?"