I'd say that family holdings are definitely a factor, specifically vineyards and olive groves, at least for the very richest. TBH, I can only provide anecdata, but most of the wine and olive producing country around Florence is owned by a few families that have owned it for centuries.
I don't doubt that the rich own nice things (and that their rich ancestors did too) but the question is whether this is causal, and I'm highly dubious, over these long time-scales.
Clark has evidence from lots of countries, and I'm still surprised just how uniform the numbers are. Even in places where private property was all-but-outlawed for 2-3 generations in the middle.
Regarding the first case, the rich don't just own nice things, the rich own assets, which means they get richer. Once you get past a certain level of wealth, you have to try pretty hard to become poor again.
As for the second, the rich have the resources to dodge or mitigate that kind of state action in all but the swiftest and most brutal of cases.
I totally agree that there are plausible mechanisms by which wealth today might help your grandkids stay wealthy. But the empirical question is whether these actually explain much of what we see. Many things which sound plausible to novelists turn out not to be very solid. And I'm trying to tell you that the data is not kind to such explanations here.
Re family status surviving Maoism or whatever: If you posit that there is something besides actual assets which is helps "dodge or mitigate", then I ask why this same something isn't in play in normal times. If it alone can explain the persistence, that weakens the case for assets mattering so much.
The other line of evidence is things like the Georgian land lottery, which elevated some people to quite significant wealth. Their kids lived well. But it's been, I forget, 150 years or something, and their decedents are no longer unusual at all.
