Age of Death coincidence?

We have recently discovered a spooky co-incidence in our family His mother was one of six sisters, and one brother. Michael's father died when he was 72, his mother died a few years later when she was 72 and last November his brother died after three and a half years in a persistent vegatative state only 3 days before his 73rd birthday, so he was 72 as well yet had had years of 'being able' to die from any number of problems associated with the PVS. At my Brother in Law's funeral I was talking to the wife of one of Michael's cousins. The cousin had died aged 72 earlier in 2011 and the wife told me that of the last 11 deaths in the cousinry family all of them had been within 6 months either side of being 72 or 72 itself. We find this a very peculiar co-incidence, as the causes of death have all been very different. We'd love to know what the chances are of Michael dying at 72, but would we really? Interesting.