Right, so as I'm reading all the highly intelligent replies (which don't actually say anything apart from 'we're right you're wrong'), I can see that 2 of 30 in the same room sharing a birthday is a definite statistical probability, whereas 2 from 40 sharing the same christian and (uncommon) surname is simply too absurd to be considered a statistic.
Truth be told, both are simply coincidences, bugger all to do with statistics.
P.S. question regarding members birthdays still not answered
. . . and probably won't be