The July 11-12 protests saw thousands take to the streets in towns and cities across the island, many denouncing the communist-run government and shortages of food, medicine and electricity at a time when cases of coronavirus were soaring.
Human rights watchdogs say more than 1,000 people were arrested following the protests. Trials for those accused of serious crimes began in mid-December and some have already led to prison terms of more than 20 years, according to the groups and interviews with families of the accused.
Cuba's government did not respond to a Reuters request for comment on the trials.
Authorities on the island, however, have previously said those arrested were guilty of crimes including public disorder, resisting arrest, robbery and vandalism. Cuba blames the United States for funding the July unrest and fanning it.
In the poor Havana district of La Guinera - where a march on July 12 was followed by vandalism, a confrontation with police and the only death during the unrest - Reuters spoke with more than a dozen residents who said neighborhood youth who joined the rallies now faced stiff prison sentences.
They denied any larger plot against the government and said the decision to march had been spontaneous.
Emilio Roman, 50, told Reuters his two sons Emiyoslan, 18, and Yosney, 25, as well as his 23-year-old daughter, Mackyani, had joined the July protests and now faced 15, 20 and 25 years behind bars, respectively, if convicted. All three have been in jail since mid-July, Roman said.
"Everyone went out because of the noise, as if they were going to have a party, but nobody thought they were going to act so severely," he said.
"The number of years (in prison) they are seeking, it's as if they were terrorists, murderers. They are my only three children," Roman said, fighting back tears. "It's a lot of pain."
Another neighbor, Alcides Firdo, 47, said his son, Jaime Alcides Firdo, 22, was initially detained for public disorder after he allegedly threw rocks during the July 12 march, but that the charges were later upgraded to sedition.
The state was now seeking to imprison his son for 20 years in a trial slated to begin on Jan. 17, Firdo said in an interview with Reuters.
"I don't understand it," he said. "You kill a person (in Cuba) and they give you 8, 10, 15 years, and now for throwing a rock you're going to throw them in jail for ... 20 years? That's an injustice."
Reuters could not independently confirm the details of the two cases with authorities as court officials do not routinely speak with the media in Cuba, nor was it possible to contact the defendants.
Laritza Diversent, director of U.S.-based human rights group Cubalex, said Cuban authorities had ratcheted up penalties to make an example and stifle future protests.
"The government is saying, 'Look, I'm not playing games ... if you go out again to protest this could also happen to you," she said.
Several rights groups, including Cubalex, say penalties for dozens already sentenced including for sedition have ranged from 4 to 30 years behind bars.
Reuters viewed several sentencing documents from trials in December in which penalties ranged from 2 to 8 years in prison for protesters convicted of crimes including disobedience, public disorder and assault. None of the convictions reviewed by Reuters were for sedition, which carries the heaviest penalties.
Not all those who took part in last year's demonstrations have faced harsh penalties. Cuba recently dropped charges against several artists who protested in front of the Cuban Radio and Television Institute on July 11, according to a Facebook post by historian Leonardo Fernandez Otano.
He said race and poverty had weighed on the process.
"I am grateful," Fernandez Otano wrote on social media after the charges were dismissed. "But I am also sad, because the young people of La Guinera have not had the same luck and are condemned to unjust and politicized sentences."
The Cuban government has said it respects the rights of all those detained following the protests, and that the steepest penalties would be reserved for repeat offenders and the most serious crimes.
(Reporting by Marc Frank, Mario Fuentes, and Nelson Gonzalez; Additional reporting and writing by Dave Sherwood; Editing by Daniel Flynn and Daniel Wallis)
By Marc Frank and Mario Fuentes