Just because your parents had you, doesn't mean that your parents like you, or even wanted you. Kyoya Otori learned this at a very young age. He was the youngest child out of four that his parents had, and there was a huge age gap between him and his siblings. His older siblings were 12 years, 9 years, and 6 years older than him. Yes, Kyoya Otori was the unplanned child. The one that they never wanted. The unloved youngest child who never got his chance to shine because he was always being outdone by his siblings. There was nothing he could do to impress his parents, everything he could ever do to impress them had already been done before by his siblings long before he was even born.
It would seem as though Kyoya never stood a chance, and it when it came to his siblings, especially his brothers. Kyoya didn't even compare. Sure he was bright and intelligent, he was the top of his class, however so were his brothers and his sister before him. He tried everything to outshine them, even succeeding and managing to run a successful host club with his best friend Tamaki Suoh, who he just so happened to be in love with. Of course Kyoya could never tell Tamaki about his feelings, yet alone hope to receive them. Someone of Kyoya's standard was expected to marry well and have children with a woman, not a man. If people knew about his homosexuality than he would be outcasted not only by his family, but by society as well. Kyoya couldn't bring himself to do that. Even if his sister would be the only one to accept him as he is, Kyoya couldn't risk it. Thus he was forced to live in a live that would deem almost cursed, for he was The Third Son.