I extract part of the passage:
There are just two people left who can speak it fluently – but they refuse to talk to each other. Manuel Segovia, 75, and Isidro Velazquez, 69, live 500 metres apart in the village of Ayapa ... people who know them say they have never really enjoyed each other's company.
who can speak it fluently has to be a restrictive relative clause.
It is unlikely that a village can have only two people. It is also unlikely that people who know them, shown above, and son and wife in paragraph 5 are not living there.
Edit
If "who can speak it fluently" is a non-restrictive relative clause, it would mean the village has just two people. As I have explained, that is unlikely.
There seems to be a clarification about this story.
Wikipedia
In 2010 a story started circulating that the last two speakers of the Ayapaneco language were enemies and no longer talked to each other. The story was incorrect ...