Is the Kennedys a Genetic Disease?

There are no studies of whether more bad things happen to the kennedys than you'd xpect from chance. But let's suppose there are, that they really have suffered more misfortunes than other families would the next question we'd need to ask would be whether there could be a natural cause for those calamities. For example, suppose you notice that in a particular family, let's say, the descendants of queen victoria of england, that a surprising number of them have a problem in that they bruise really badly and bleed for a really long time if they get cut. You might suspect that there's some kind of supernatural curse at work, but there isn't