“What are valid reasons to break up?”
If you are talking about
breaking up a marriage on a permanent basis, the only possible valid reason given in scripture is
a spouse engaged in a sexual perversion. Usually this is limited to adultery, but
the Greek term the Lord used in Matthew is a fairly broad one, and there could be
several other sorts of perversion that qualify.
Sorry, that’s a bit grim, but there you are. However, I suspect you are inquiring about a dating
relationship or perhaps an engagement. In that case, I believe the Bible’s
answer would be a little different.
Frankly, almost anything qualifies.