What an unlucky family...they're always mourning an untimely death due to lung disease while nobody smokes

A wealthy widower, with 3 daughters ranging in ages from high-school freshman to college senior, five years after his wife passed away, married a young widow of 29. She had no children from her first marriage and never had any in her second. It seemed that the mourning never ended in his family ever since she walked over the threshold. His new wife's brother's wife died of a lung disease, as did her husband's sister, as did the oldest daughter's husband. It was like lung disease ran in the family, except all of the dead were not related by blood but only by marriage. Clearly, genetics is not the root cause here, so it must be environmental. And not one of the deceased had ever smoked.

                                                                                                - SDG