Maybe? That's a really complicated question honestly - how much of their personal property actually is hereditary wealth and how much is a benefit of their station. I can tell you the answer is neither 0% nor 100% - the royal family (if dethroned) shouldn't be thrown out as paupers and it shouldn't be granted personal control of spaces that enjoy public use. Where precisely that line should be drawn is complicated but if that line leaves them with any significant portion of their current titular wealth the UK will end up losing money. The Crown Estate might be worth around 15.6 Billion, so a few hundred million every year is far less then the family would receive if they liquidated the lands at value and just invested it into an index fund. The actual income of the estate is significantly higher - with a lot of those assets under reporting their actual yield in terms of tourism and public benefits.

I think it's a really complicated question.

Lastly, while we're on this topic - why hasn't the US seized the wealth of the 100 most wealthy individuals unilaterally - that money would be of immense amount of benefit to the country so why do we let wealth accrue?

King Georges stamp collection is worth 10s of millions. It’s also 100% private property.

When King George died, his stamp collection went to his widow, who kept it until her death at 102.

There’s probably personal property like that scattered throughout the family tree.

It's a complicated question with regards to some of their property. It's not at all complicated with the Crown Estates. That is clearly public property. Otherwise Edward VIII would have kept it when he abdicated.

Edward VIII was pressured into giving up a lot of stuff he legally should have been able to keep.

He wasn’t good at making decisions.

"Legally", based on laws made law by kings of previous generations. The whole point is people asking to change the laws, democratically.

if the government tried it they'd take it to judicial review

and they'd win