Translation:My great-grandfathers bought this level land.
I don't like the translation of either level or flat for "ebena". In English, there is a subtle, but very important difference between level and flat. A table can be flat, but not level. It could also be both flat and level. The definition for "ebena" in PIV more closely translates to that of flat. Level would be better put as "horizontala," as found in the PIV. I don't know that I would go as far as to say this definition is wrong, but I certainly believe it is not an optimal translation.
By saying "praavoj" does this sentence mean the literal relationship i.e. the father of my mum/dad's mum/dad? And then more than one of these? As though four male friends bought some land together and two of them had a boy, two had a girl, these children partnered up and the two couples happened to have a boy and a girl and these partnered up and became parents to the speaker of this sentence?
Or does it just mean "forefathers" in a very general sort of way? (Which is what I assume given the complexity of the inter-marriage scenario.)
EDIT I discovered that ancestors is accepted but forefathers is not.