But waiting on the dock in 1994 for the arrival of Jonathan and Daniel, Amadeo was filled with hope again. The father and sons, reunited, embraced.

While they could not speak the language, Amadeo was eager to bring his sons back into the traditions of their people. He and Jonathan woke at 5 a.m. for the hunt, returning after sundown. He took the boys to what remained of the Taushiro settlement in Aucayacu, where only his father and a few relatives still survived.

Jonathan felt apart from it, unable to communicate with anyone there.

“My grandfather could only say my name,” he recalled. “I had gotten used to Puerto Rico. Now I felt more from there. I cried all night.”

The opportunity to learn Taushiro seemed lost. The boys were teenagers, past the age when children usually pick up language quickly from their parents. Spanish was still the language they heard at school most of the day, and a stigma lingered in Intuto when it came to indigenous languages.

“I could barely say a few words — mother, father, that was it,” Jonathan said.

The arrival of David, the oldest brother, in 1996 brought new challenges. Mr. Villalobos, the Christian missionary who directed the school in Intuto, said David’s anger had followed him to Peru. The boy rarely did his schoolwork and was known for carrying a knife around town, once threatening to stab one of his classmates, Mr. Villalobos said.

And Amadeo’s drinking continued.

One day, José Álvarez, a missionary, went to visit Amadeo at his home on the edge of town. In Spanish, Amadeo told him he was sick, but after a moment Mr. Álvarez said he realized Amadeo was trying to say he was depressed, unable to find the correct word. Amadeo began to cry, the first time Mr. Álvarez had ever seen him express emotion.

“He spoke in tears of his children, that they didn’t want to come see him, that they didn’t want to know hardly anything of him, or their Taushiro origins, not the language, not the culture,” Mr. Álvarez wrote in a letter from that time.