Brother who has past trauma due to rejection from his father, sleeps around and doesn’t believe in love until his sister gets a boyfriend. The boyfriend is sweet and kind, and so the MC falls in love with him, but he buries his feelings because he doesn’t want his sister hurt.
http://www.mangago.zone/read-manga/i_want_to_become_your_bird/
Brother who has past trauma due to rejection from his father, sleeps around and doesn’t believe in love until his sister gets a boyfriend. The boyfriend is sweet and kind, and so the MC falls in love with him, but he buries his feelings because he doesn’t want his sister hurt.