I don't think there is a legal basis for a strictly genetic claim on land tenure. The argument has been more along the lines of ethnicity or "sense of nationhood," more broadly defined.
In some ways it's analogous to my learning in grade school that "our Pilgrim and Puritan" forebears settled in New England, and "our American founding fathers" adopted the Constitution.
I have zero - 0 - Pilgrim/Puritan forebears; when "our" founding fathers were adopting the Constitution, my ancestors were in Rheinpfalz.
Nevertheless it makes a kind of sense to teach history that way to American school children, since it tends to bind us into a shared past, a shared sense of nationhood.
Lose that, and you end up with --- what we have: the centrifugal disintegration of nation, based on "Black history," "La Raza history," "the Americo-Muslim heritage," etc. etc. This is no way to build a nation.
Do not think I am saying here that minority histories and perspectives must be excluded. I myself am scandalized that Catholic history is simply not taught at the classroom level in America, not even in Catholic schools. I am simply saying that nationhood is more generated by shared stories than by shared DNA.
Back to the topic: UNESCO's words were lies; the Pope's words --- in the narrow sense of "what he actually said" --- were true. I'll vouch for that.
But if we're talking about the "people of Israel" as a coherent group, then what exactly are we talking about here if not genetics and ethnic background? It seems to me that this "sense of nationhood" you're talking about is so broadly defined that people who may be of completely non-Semitic background may now be considered Semites. If a German converts to Judaism, does he now have a claim to the Holy Land? What made the descendants of Abraham so special if not their heritage?
“I am simply saying that nationhood is more generated by shared stories than by shared DNA.”
Matthew 1:1 indicates a different perspective.
Genetic citizenship: DNA testing and the Israeli Law of Return
http://jlb.oxfordjournals.org/content/early/2015/06/16/jlb.lsv027.full
“...After the news of this one student’s experience made headlines, the Israeli Prime Minister’s Office confirmed that many Jews from the Former Soviet Union (‘FSU’) are asked to provide DNA confirmation of their Jewish heritage in order to immigrate as Jews and become citizens under Israel’s Law of Return....”