Cachorro

As a favor to his hippie sister who has gone off to India, Pedro, a gay dentist, has agreed to look after his nine-year-old nephew, Bernardo. Bernardoâs father is dead and the boy and his uncle have not had much to do with each other until now. Originally, the boy was to stay with Pedro for a few days, but six weeks have passed with no word from the boy's mother.
His nephewâs presence forces Pedro to take a break from his otherwise extremely active sex life. In fact, Pedro was beginning to tire of the superficial nature of his many relationships. Even his boyfriend, Manuel, who suddenly pays Pedro a visit and who shares his penchant for leather and latex, is not really the man with whom he wants to spend the rest of his life, although they express love for each other. Then, all at once, an entirely different set of problems crops up. For one, there is DoÃ±a Teresa, Bernardoâs paternal grandmother, who one day darkens Pedroâs door and puts the emotional screws on him. Worse still, however, is the news that Bernardoâs mother has been arrested in India for drug smuggling. She may be facing a prison sentence of thirty years, so the embassy informs Pedro. Pedro is just as shocked at this news as Bernardo; nevertheless, he realizes that he is now responsible for the boy. Without further ado, he decides to rise to the challenge this represents. There suddenly seem to be so many things to organize â such as repairs to the house and finding a school for the boy â that Pedro hardly misses the life he used to lead. Gradually, however, he succeeds in rekindling his sex life â albeit in a less excessive form.
Then DoÃ±a Teresa puts in another appearance, this time demanding custody of Bernardo. But Pedro is ready to fight for the boy's welfare. After illegally obtaining his medical history (revealing that Pedro is HIV positive) and hiring a private investigator who obtains pictures of Pedro on a night out in a gay club, and threatening him with both, he ends up letting her put Bernardo in a boarding school. When his grandmother goes to visit him later on, revealing Pedro's HIV status (despite their previous agreement), Bernardo reveals that he already knew from his mother, and that his mother was HIV positive as well. She then reveals that he is in the hospital with pneumonia. He then tells her that he hates her and that it's her fault that he's currently in the hospital, because he wasn't there to care for him.
Three years pass, during which several letters go back and forth between Bernardo, Pedro, his mother and his grandmother. We then see Bernardo and two of his friends, a boy and girl, at a funeral, and a casket being lowered, although it is not immediately revealed whose funeral this is. Shortly after, a cab pulls up with Pedro inside, out of the hospital and healthy, and he expresses lament at the passing of Bernardo's grandmother. After a brief conversation, Bernardo returns to his two friends, kisses both, and parts from them, leaving the viewer to wonder whether or not he's romantically involved with one of them. Bernardo then returns to his uncle and they ride away together in the cab.

Question: How many years pass during which several letters go back and forth between Bernardo, Pedro, his mother and his grandmother?
Answer: three