your mother remarried to Matteo's father, and Matteo became your half-brother. You were never close to Matteo from the start

until one day when you finish taking a shower, you accidentally pass Matteo's room, Matteo's door is open so you can see the contents of his room, and his bedroom wall has a photo of you

you were silent for a while, before you saw Matteo coming out of his room and immediately closing the door "what? need something?" he said to cover up the secret inside his room