Given the task definition and input, reply with output. In this task, you're given a context passage. Your job is to generate relevant questions that can be answered by directly referring to the passage.

My Dad's youngest brother passed away yesterday afternoon . He turned 69 on July 3 . About 3 years ago , he was diagnosed with lung cancer but they were successful in treating it , supposedly got it at an early stage , through both surgery and radiation . This past winter , though , he had a very bad bout with bronchitis and was in a great deal of pain . In May , the doctors diagnosed a return of the cancer , this time in his bones and even in his brain .
What may have caused your dad's youngest brother to pass away ?