re: Doubt this has happened to a TDer before.

From a strictly utilitarian point of view, your wife's biological grandchildren have the right to know what, if anything, runs in the family disease wise - diabetes, heart failure, cancer, etc...

Your wife should get in touch with the widow to disclose this information, if for no other reason.

My mother and her brother were adopted. He recently died of pancreatic cancer with no knowledge of it running in the family. They've never made contact with their real father's family out of spite. I recently told her "frick that", I am leading the efforts to do so to find out what other diseases my siblings and I don't know we are at risk for.