Felis always felt that Russell didn't genuinely have no idea about his existence.
After all, they spent a few years together in the apprentice dormitory, even though they didn't study in the same room, but... living in a small building together, how could he not know who he was?
It's just that for Russell, relatives like him might as well not exist.
Although Carpenter seems to be the one who only befriends useful people, with a heart as hard as iron, in reality, it's Russell who genuinely doesn't even glance down.
But he doesn't lack feelings entirely, he just prefers responding to others, rather than giving himself.
A typical mage personality... you give first, and then he'll choose whether to respond.
Once Carpenter offered his love and he accepted and reciprocated it, that bit of possessiveness as an elder brother emerged... not necessarily blocking all external emotions, but definitely wanting to eliminate all negative elements for his sister.
