A) I once heard that there are three side to the story.
1)his side
2)her side
3)the truth
There is a fourth side as well. THE REAL TRUTH.
B)They decided to break the engagment rather than take the risks.
They could STILL have checked with Dor Yesharim – what if everything was ok with their DNA – they could always break it off a few weeks later, if they so desired. I think that was a precipitous action to just break up without knowing for sure.
Here’s a question, though. I was always under the impression that to break tenoim was the equivalent of giving a GET, and that the girl could not marry a Kohein after that. Is it true that she must be qiven some type of “GET?” This is (so I was told) why tenoim are done generally only just before the chuppah, in most circles. In any case, a broken egagement is FAR,FAR,FAR better than a broken marriage. It may not always be easy to find new shidduchim after an angagement was broken, but it is still easier than redding shidduchim to women who were married and divorced, and who possibly have a child or two as part of the deal. When they are in their early twenties, most age appropriate guys will not want this situation, unless they, too are divorced and possibly have a child.