What is the largest piece of property that has been held by the same family for the longest time? I’m guessing it’s something owned by a member of the British nobility. What about something that isn’t owned by a queen, duke, or earl?
By private property I am guessing you mean land and not possessions? From a fast Google I find Japans Hoshi Hotel has been in one family since 718AD. The Hoshi family is in its 49th generation. Not that large of a footprint but still impressive.
Yes, I meant land. How big is the total property?
You were close, there is another hotel in Japan that is slightly older… same family since 705AD!
What about property owned by an organization? There are probably a fair number of physical relics (e.g. alleged pieces of the True Cross) that have been owned by the Catholic and/or one of the Orthodox churches for centuries.
One of the big ranches owned by one individual, not including any government graze land?
One individual, not a Royal, or corporation that started from a single man unless owned by one single person today?
Ted Turner?
Any in AU or NZ?
I’m always puzzled by these questions that have two different superlatives in them. If you have one parcel of 100 acres held for 500 years, and another for 400 acres held for 150 years, which wins?
You asked two questions: Which is biggest? and Which is longest? It is nonsense to try to ask which is both the biggest *and *longest unless by some wild coincidence one particular property is both the biggest and the longest. Much more likely there is one biggest ever, and one longest ever, but they’re two different properties. ETA: or what chrisk said just a moment before.
At any rate …
We’ve got some answers for longest.
The ranchos of the old Spanish West of what’s now the US are some decent contenders for biggest, although most don’t exist now. See Irvine Company - Wikipedia as an example that was once 185 square miles in extent.
The XIT Ranch in Texas (extant 1885-1912) was about 3,000,000 acres (200 miles north/south by 20 to 30 miles east/west), or around 12,000 square kilometers / 4600 square miles.
I’m going to arbitrarily say longest held wins. But I’m open to a compelling opposing argument.
Gardiners Island (NY) may be, in North America.
More info here. It’s 6 miles long, though I guess that’s not really what you mean. 
No, that’s a perfect example.
Hohenzollern Castle has been owned by the Hohenzollern family (actually by the two branches of the family) for more than 1000 years.
The above is not correct:
http://www.burg-hohenzollern.com/castle-history.html
(the official website)
Neither of the hotels would be a big enough footprint. I know some of the Northwest Ordinance grants are still in the same families since 1781 or 83 but those would be more in terms of 40 acres or so; even the intact ones wouldn’t be much over 100.
Pfft! The Anna Creek cattle station in South Australia is 24,000 sq km, which makes it larger than the State of Israel.
The award for “longest-held” is certainly not going to any property in the New World. There would be estates in England still occupied by the same family on the basis of a grant by William the Conqueror following the Norman invasion in 1066. And there are certainly many properties occupied by the same family on foot of a grant of land following the dissolution of the monasteries under Henry VIII. And I dare say there would be analogous situations in other European countries which have not been subject to invasion and colonisation for even longer periods.
There are older British estates which were owned by knights who turned coat and gave aliegance to William. The Grevilles, present occupants of the Earldom of Warwick were one such family, but their land ownership appears to have changed over time.
Doesn’t New Mexico have land grants running back to the 16th-17th centuries?
The OP was looking for “something that isn’t owned by a queen, duke, or earl.”