I am not surprised that people will reject a shidduch because of a sibling. There are schools that will reject a girl because of an older sibling. In both cases, the boy has lists….the schools have so many applicants. This is the reality.
The truth is that in the case that Yiddishekup 101 wrote about, would the family of the girl really want a family that has a problem with her brother? Clearly this is not her beshairt, leave it and move on.