Karma never had his parents around him growing up.

While Gakushū didn't have proper parents.

Karma is neglected while Gakushū's father is emotionally unavailable. So growing up our boys were mostly left alone :(

Gakushū's dad may be around but that doesn't mean their relationship as father and son is great. Quite frankly Gakushū is treated not as Gakuho's son but as just his student. Karma and Gakushū can lean on each other, they know what it's like to be alone, having bullshit parents.

I can imagine that this will be the first thing they'll bond over. It's sad though