I have to assume that Boris is the runt, but he seems oblivious to it. Following and often leading his brother into adventures, pouncing as often as being pounced, Boris is gifted with an even-tempered manner that suits Annabelle and myself and balances Arlo's intense energy very well.
I go out of my way to treat him as though he is big and powerful to instill a sense of confidence, purpose, and substantiveness. So I don't knock him down or lift him as often as I would like to, and I move out of his way when I see him coming or he wants to get up.
Boris announces himself and his ideas as he walks around with little tribble-like noises, rarely if ever actually meowing. He leaves that to his brother's insistence and Annabelle's occasional call to play.