You may have passed as caretaker, but you have failed as family.
Well..I agree with Lei..
I completely agree, but I think that there needs to be a reminder that things like lack of communication does happen in real life. Not apologizing may just be a part of how their family functions, or he may not know how to apologize to his younger brother and not apologizing in the earlier stage led to not apologizing at all because the moment was missed. That Tatsuya cleared up the misunderstanding is not an uncommon thing in that sort of situation either. I'd like to think that he was able to bridge the gap between the two brothers.
Being an older brother in college myself, I have to say that his conduct regarding his younger brother was very poor to say the least. Working full time and all, yeah it is stressful and sometimes you need to let it out. Having to leave behind friends, miss all the opportunities, and take care of someone is very tiring and is going to be a cause for resentment. But not apologizing nor acting as an caring older brother to your siblings is not really acceptable either.
People aren't animals that just require food, water and shelter just to be okay. There are some social roles that are needed to be played as well. Missing people in one's life means that the remainder have a greater responsibility to pick up where others left off.
It sounds self-righteous and all, but it is the right thing to do and is something I would try my best to follow. I like my brother very much, so I would try to least keep him happy or content. I don't want him to hate me, or even worse be scared of me.