His father, Santiago Mari Ramos, was an active participant in the independence movement who often took his son to political meetings and rallies.

In 1943, when he was 18 years old, he founded a pro-independence movement called "Capítulo de Agregados Pro Independencia",[2] in his high school along with some of his friends, in Mayagüez.

In 1948, the university's pro-independence student body invited nationalist leader Pedro Albizu Campos to the Río Piedras campus as a guest speaker.

Mari Brás was one of the student leaders who chanted anti-American slogans and who marched with a Puerto Rican flag in his hand.

Mari Brás and others who protested were expelled from the university; he was arrested, jailed, and let go three times in response to his revolutionary activities.

[6] On January 11, 1959, Mari Brás founded the Pro-Independence Movement, which grouped Puerto Rican independence followers who supported the Socialist philosophy.

[7] In 2009, thanks to the Freedom of Information Act documents were obtained by news stations, Primera Hora, that showed the FBI knew of a plan to assassinate Juan Marí Pesquera, and had not warned him.

)[8][9] After losing his son and the election, Mari Bras continued to dedicate his time to campaigning for the independence of Puerto Rico.

[11] In Lozada Colón v. U.S. Department of State (1998), the plaintiff was a United States citizen, born in Puerto Rico and resident of Puerto Rico, who executed an oath of renunciation before a consular officer at the U.S. Embassy in Santo Domingo, Dominican Republic.

The court does decide to not enter to the merits of the citizenship issue; however the U.S. District Court for the District of Columbia rejected Colón's petition for a writ of mandamus directing the Secretary of State to approve a Certificate of Loss of Nationality in the case because the plaintiff wanted to retain one of the primary benefits of U.S. citizenship while claiming he was not a U.S. citizen.

The Court described the plaintiff as a person, "claiming to renounce all rights and privileges of United States citizenship, [while] Plaintiff wants to continue to exercise one of the fundamental rights of citizenship, namely to travel freely throughout the world and when he wants to, return and reside in the United States."

According to the State Department, U.S. Immigration and Naturalization law stipulates that anyone who wants to give up their U.S. citizenship must live in another country.

Former Puerto Rico Supreme Court Associate Justice and former Secretary of State Baltasar Corrada questioned the legality of the certification, citing a law passed in 1997, authored by Kenneth McClintock Hernández, which establishes United States citizenship and nationality as a prerequisite for Puerto Rican citizenship.

[17][24] Later in his life, Juan Mari Brás retired from active politics and no longer acted as president of the defunct Puerto Rican Socialist Party.

He dedicated his later years to seeking unity among the varied pro-independence factions in Puerto Rico and appeared before the United Nations on the political status issue.

After hearing of Mari Brás's death the mayor of the city of Mayagüez, José Guillermo Rodríguez, decreed five days of mourning and ordered that flags in all municipal building be flown at half mast.

[26] Mayor Rodríguez also announced that the city of Mayagüez would be collaborating with the Hostos School of Law in the funeral arrangements.