I know UNESCO endeavour for WHS to not be in private hands, but I'm sure there are some that are. The Swedish farmhouses, Palace Stoclet, Blenheim Palace .... but perhaps I have missed the nuance.
Quite right - and there are of course many WHS which contain private property mixed with government owned property. There is absolutely no reason why a privately owned property can't be inscribed - BUT the owners have to accept the limitations which thereby arise regarding what they can do with the property. Whether these are that much more onerous after inscription than before depends very much on the legal framework operated within the country. I can't imagine that the 11th Duke of Marlborough faces much greater hassle if he wants to build a hotel in the grounds of Blenheim Palace because his building is inscribed than he would if it wasn't as UK laws controling what can be done with listed buildings is very strict! The same may not be true for an erstwhile Maharajah in India of course. I suspect that ICOMOS want to see government owned buildings in countries where the general legal framework controlling what owners of private property can do with it is rather weak - as may be the case in India
If you watch whc 2012(available in youtube) it is clearly said that the properties owned by erstwhile maharajs can't be granted for OUV. Therefore these sites are not included in whs nom of hill forts of rajasthan
Actually the ICOMOS representative this year came back on this issue and emphasised that, in making the suggestion for a future extension to the property in the form of a fort belonging to an ex-maharajah, there was absolutely NO implication that the property should be taken away from him and "nationalised"!! Indeed in reaching the agreement that the draft WHC decision on this matter should be changed to remove this aspect the comment was made along the lines that "maybe at some future time he may change his mind" - so it would appear that ICOMOS/UNESCO don't see "nationalisation" as a prerequisite for inscription - even in India!!