Responses
Are you looking for a specific manga that you just forgot the title or are you looking for any manga with this plot?
That is too specific but I'm sure there will be mangas out there that fit your description. I know exactly what you are talking about because I've recently finished reading The Best Smell.
Sorry if I'm not being clear, I'm looking for manga with this kinda plot.
Any manga/webtoon like 'the best smell' and 'nanohana boys' ...Where one (let's just call him B) grew up in a harmonious family, while the other one (let's call him C) was being abused/hated by his family member.
Then because B had only knew love while growing up, he was so angry after knowing that C was being mistreated. He couldn't understand as to why ones would hurt their own blood.
B would try to help C, even go as far as to confront C's abuser.