WolfishMusings-
If a person is blind I think we both know how it could affect a relationship.
If a person is not a carrier for a particular disease, the status of that persons’ spouse is irrelevant, so there is no need to inform her.
Letting it be known that members of his family are carriers may create a stigma against the family for a trivial reason.
(Do you honestly feel that everyone would give the same chance to a known carrier as to one whose status is unknown?)
Another case I know of personally- this has nothing to do with Dor Yeshorim, I was consulted to interpret the statistics from the different geneticists involved- the mother of a potential spouse was concerned about the possibility of the other family having the genes for a genetic disease.
Despite the fact that the geneticists were able to prove 100% (not close to 100% but actually 100%) that the disease was a fluke and not hereditary, and despite her family being told by their rov and their own geneticists that not only should they go ahead with the shidduch, but if their own children were in the same situation they would also go for it- they broke it off.
(Interestingly enough, due to the extensive genetic testing, had they gotten married the chances of them having any children with the same disease would have been less than another couple in the general population.
I explained that according to their [distorted] mathematics, the chances of them having a child with the disease was one in 8,000,000,000 (8 billion), the mother explained that she would like her daughter to have 10 kids like she did so the overall odds are only one in 800,000,000 (8 hundred- million).)