Regarded it as their own, and all that.

'Proprietary rights' theory, passed on from fathers to sons.

Then Standish and Hade leased the land, having gotten a better hint as to where the treasure was.

And that got the Caesars riled.

Then the Caesars get an inkling that Standish and Hade have actually located the treasure and are sneaking it to Standish's house, bit by bit.
And then they go still-hunting for the despoilers and for their ancestral hoard." "Why!" cried Claire, astounded.