Final answer:
When Bayardo buys Xius' house, Xius' widower's past happiness is lost due to his father's death and the need to mourn.
Step-by-step explanation:
When Bayardo buys Xius' house, Xius' widower's past happiness is lost. In the passage provided, it is mentioned that Xius and their wife had a happy and prosperous life together. However, the husband grew sad and explained that he had a presentiment that his father was either dead or dying, and he needed to mourn at the grave. This suggests that the husband's sadness and the loss of his father affected his past happiness.