When he go for what he wants (advertising) the parents didnt even celebrate and instead criticised him and told him to follow his older bro footsteps and go business. While his sister got praised for and even celebrated it. The unfair treatment probably build up and made him really frustrated and betrayed and seeing his sister being happy made him so bitter he couldnt hold back the tears or smth. Just the usual stuff every middle child goes through. 24/7 jealous of your siblings cus they hv it so much better than u. And doubt ur self-worth constantly want to test if the parents would care if u had killed urself. So yeah its probably becus his sister got praised while he doesnt
Was it because his sister got praised for university choice where as he got criticised by his parents?