I know that there are at least a couple yaoi that are like this. I have read at least 2 that are however I can't seem to find them in my lists. Maybe I am just simply overlooking them. So this is what I am looking for.

Either the seme/uke is stolen away from a sibling. I Want to Become Your Bird is a great example.
Or the uke/seme's sibling brings fiance/boyfriend/friend home and it turns out that the seme/uke either had a relationship with the boyfriend/friend or has a crush on the fiance/boyfriend/friend.

Hopefully the description of what I am looking for isn't to hard to understand. >.< Even if you have a yaoi in mind that may not be exactly what I am looking for, please go ahead and post it. I am running out of yaoi to read. Thanks in advance for the suggestions.

*Edit ~ I am totally okay with tragedy, smut, incest and pretty much everything else *

Thank you, that is the one that I have read but couldn't find