Forbidden Love Yaoi

Stepbrothers
Aki lives with his younger stepbrother, Saku, while he's attending university, but when Aki gets frustrated by Saku's playboy ways and complains kissing doesn't feel good, Saku offers to show him a kiss that does, and things escalate from there.

Stepbrothers
Haruhi has had enough of his bratty younger stepbrother, decides to move out, but surprise surprise, his brother moved with him.

Stepbrothers
Souji is adopted and feels like a burden, Jin is a playboy who kisses Souji to see him panic for "stress relief," but when Souji announces he's moving out, Jin straight-up rapes him. And somehow they get to a relationship from that.

Stepbrothers
Continuation of above.

Stepbrothers
Hisaki lives with and provides for his younger brother Yuzuru, but when he starts to develop feelings for his brother, Hisaki starts working as a dominatrix-style call boy to deal with it.

Stepbrothers
Yuuto's loves his cool, new older brother, Ryuusei, but when he sees Ryuusei kissing a man he has complicated feelings about it. Now in college, they're living together and Ryuusei refuses to let the distance between them stand.
Trigger warning: mild incest (by marriage)

Stepbrothers
Younger brother worries that his older brother will find out about his feelings and hate him, moves out on his own, older brother chases him.

Stepbrothers
Asuka and his younger stebrother Yui were best friends until they got stuck in a locker in an abandoned building years ago, and ever since Yui is arrogant and cold. But what really happened that day?

Stepbrothers
Diligent older brother and rebellious younger brother. Now that it's time to go to college, older brother decides to break the rules.

Stepbrothers
Childhood friends/neighbors and owners of a flower and a liquor shop become stepbrothers.