I suppose if you're counting the people born into, then yeah, but for the people that actually made the wealth....well very few of them didn't involve a lot of hard work. A few young artists, maybe, but if they were unable to work hard they probably didn't keep that wealth.
What I meant is along the lines of: there is no situation where hard work can't help - but just through hard work alone the chance of becoming wealthy is small. So my opinion is that luck played a bigger role than hard work for most of the rich.
Plus there are plenty of types of hard work that don't lead to wealth, like caring for children, but are still necessary.