I don’t know why you’re posting this as a topic in here rather than a question on the homepage, but I think the manga you’re looking for is Camellia.
http://www.mangago.zone/read-manga/camellia_minami/
HOLY S*IT THANK YOU SO MUCH
I don’t know what a topic is? I’ve been using this site for a long time and still don’t understand it(づ￣ ³￣)づ
You’re posting under a specific manhwa, usually this section is for people who are reading this specific content. If you tap the manga go button at the top it’ll take you back to the home page. There’s a place there to post general topics and etc. like “looking for”
So I don’t remember the name of the yaoi but I REALLY want to re-read it and didn’t save it. It was about this black haired boy who always gets abused by his blonde older brother. They live in the same apartment and they don’t have a dad and mom if I remember correctly. They had a bad relationship with the father. The blonde older brother started abusing his brother by accident when they were younger and started to “get turned on” by it and it became a thing. Also the older bro is really possessive and if he finds any markings on his little brother he will turn possessive and ask him questions and beat him up. I’m pretty sure the point of view was the black haired little brother. THANK YOUUU