Denis's daughter, Beatriz, told AFP: "I would accept anything to have Dad back. I will negotiate anything."
A few months ago, the family collected the equivalent of $2 million in food -- at the EPP's request, she said -- to be distributed among poor villagers.
But to no avail. No word from her father.
"Every time a hostage has been able to return home, it was not because the government found them. It was because a ransom was paid," Denis said.
The EPP has proposed an exchange of the hostages for its top two leaders Alcides Oviedo, 52, and Carmen Villalba, 50, both prisoners in Asuncion.
Villalba's brother Osvaldo leads the EPP in her absence.
In 2010, documents uncovered by the Paraguayan authorities revealed links between the EPP and the since-disbanded Revolutionary Armed Forces of Colombia.
The Paraguayan government recently sought support from Colombia in intelligence and military training to combat the EPP.
In an unforeseen way, this could mean the beginning of the end for the guerrilla group.
"The Concepcion region has become a strategic place for drug traffickers, and the EPP disturbs them, because it attracts the presence of the state," said Martens.