He looks pretty good as a big brother tbh, his sister is spoiled alright. Everyone around him, including his grandma, should stop talking as if Yugami doesn't know how to love.
Love comes in many forms, people express it differently person to person, be it consciously or unconsciously. I think in Yugami's case he is doing it unconsciously and not even recognize that, thus he couldn't argue when people said he is lacking in love in teaching.. While in fact, he does have it all the time.