Is my conflict with my brother, after he assaulted me first, considered an act of disobedience to my parents, knowing full well their anger and sadness?

Allah has made obedience to parents obligatory and forbidden their disobedience. Annoying and angering parents is part of the forbidden disobedience. You must stop quarreling when your mother is angry or commands you to, and you should promptly repent and seek forgiveness from your parents. You ought to avoid quarreling and try to solve problems with gentleness and leniency.