If the life of Tsuna was different is what will happen here, he no was the son of Nana and Iemitsu but they had the same child that would be the tenth. Tsuna still has his last name Sawada. He grew up in a different environment he knew about the mafia because the family is living. He grew up in the family Hibari because his mother died when he was 3 and left the family home Hibari. Kyoya is very attached to both of them to consider brothers. Reborn will be in the eye of Tsuna and Hibari when they are alone and when conversation is spying on your student is not Tsuna and they also see these moments together and look at Tsuna is to know what is your relationship with the family Sawada because he has the same name as them.