Awhile back I read a Yaoi manga that I can no longer remember the name of. The beginning started out with a police detective breaking up a lovers quarrel after things get physical, only to discover that the victim is the younger brother of an old friend from his teens. The younger brother ends up living with the detective because of a stalker boyfriend (He eventually ends up breaking in). Later the detective discovers that his old friend started abusing the younger brother (I believe after an accident, he believed to be the younger brothers fault). If anyone knows the name of this story I would greatly appreciate it! 😕 😕 😕

This sounds like Kinjirareta Taion: http://rocaca.com/manga/kinjirareta_taion/
Here's the description: When Detective Moriyasu breaks up a lovers' spat on a street corner, he doesn't expect to know one of the guys. Kazuki is a troubled young man with nowhere to go, so Moriyasu takes him in.
Hope this is it!