Robgsr, this is not quite right. Less than 10% of prostate cancers have a proven genetic link, being associated to the BRCA genes. For everyone else, the research is murky to say the least. There is a known increased risk if a man has a father, uncles, brothers who were diagnosed at a young age - but if a male relative was diagnosed in his late 60s or 70s then there is no evidence that his sons or brothers will be at more risk. Nor is it proven that these risks are genetic - they may just as likely be environmental ... they have usually lived in the same place, drunk the same water, eaten the same food.
To put the stats into perspective, a huge piece of European research (on post-mortem of men that had died from all causes including accidental) showed that 60% of men in their 60s, 70% of men in their 70s and 80% of men in their 80s had prostate cancer, even if they never knew it. If the familial link was as straightforward as a gene, then 100% of men would have PCa by now :-(