He was instrumental in the historic and peaceful 1986 People Power Revolution, which toppled the dictatorship and ended martial law under Ferdinand Marcos and installed Corazon Aquino as his successor in the Fifth Republic of the Philippines.

[2] Sin left his childhood home and his family to study in St. Vincent Ferrer Seminary,[3] and was ordained a priest of the Archdiocese of Jaro on April 3, 1954.

On March 15, 1972, Sin was appointed Coadjutor Archbishop of Jaro, taking on administrative roles in the archdiocese, while holding the titular see of Massa Lubrense.

He became witness to corruption, fraud, and even murder by the regime and rising popular discontent with the dictatorial rule of Marcos and his wife, Imelda.

[3] Sin appealed to Filipinos of all religions to follow the teachings of Jesus in the Gospels and use peaceful means to change the political situation in the Philippines.

Beginning in the 1970s, Cardinal Sin, a moderate, was among the leaders who publicly pressured President Marcos to end martial law, which had been imposed in the belief that leftist radicals would overthrow the government.

[6] In February 1986, Sin called on Filipinos to surround the police and military headquarters in Manila to protect then-military Vice Chief of Staff Fidel Ramos, who had broken with Marcos.

In what later became known as the People Power Revolution, Marcos, his family, and close advisors were forced to flee the Philippines[6] and took up residence in Honolulu, Hawaii, US, on the invitation of U.S. President Ronald Reagan.

Poor people marching in the streets, with the support of Sin, the elite, and military generals, succeeded in toppling Estrada from power and elevating Gloria Macapagal Arroyo as acting president in what was perceived by the international community as a "triumphant" democracy.

[10] Hours before hundreds of soldiers and officers staged a failed revolt against President Gloria Macapagal Arroyo in July 2003, Sin urged Filipinos to be vigilant against groups plotting to violently overturn the country's democratic institutions.

Afflicted for years with a kidney ailment brought on by diabetes, he was taken on June 19, 2005, to the Cardinal Santos Medical Center in San Juan, Metro Manila, because of a slight but lingering fever.

[17] As the incumbent Archbishop of Manila in 1996, when the government distributed condoms to curb HIV infection rates, Sin called the programme "intrinsically evil",[18] in line with Church teaching on the matter.