The guerrilla-turned politician was born in 1955 in the southern Colombian town of Florencia, Caqueta.
At 22, Marin joined the youth movement of Colombia’s Communist Party after which he entered the ranks of the FARC.
By 1985, the guerrilla has risen to become the political adviser of the FARC’s 14th Front.
The FARC agreed to form political party Patriotic Union in 1984 as a political way out of the armed conflict. Marin joined the party and was elected into Congress in 1986, the same year that later-President Alvaro Uribe was elected Senator.
However, the Patriotic Union fell apart as thousands of its supporters and dozens of leaders were assassinated and Marin returned to the jungle, now promoted as commander of the FARC’s Southwestern Bloc that operated in the departments of Huila, Caqueta and Putumayo.
Following the death of FARC founder Jacobo Arenas in 1990, Marin was elected member of the FARC’s Secretariat, the guerrilla group’s highest political and military organ.
Marin took part in the 1999-2002 peace talks with the government of former President Andres Pastrana and in 2007, when Venezuelan President Hugo Chavez attempted to negotiate the exchange of FARC hostages for incarcerated FARC rebels, the rebel leader traveled to Caracas to negotiate with representatives of the Uribe administration.
Following the 2008 killing of Raul Reyes, unofficially the FARC’s foreign minister, Marin assumed that position. According to the Colombian government, Marin at that time was operating from Venezuelan territory.
After the FARC’s then-supreme leader Alfonso Cano was killed in 2011, Marin was mentioned as a likely successor because of his seniority in the group. The secretariat however decided to elect “Timochenko” to lead the rebel organization that had come under increasing pressure because of their military losses and the death of some of their leaders.
In 2012, the FARC included Marin in the team that would negotiate peace with the Colombian government in the Norwegian capital of Oslo and the Cuban capital of Havana.
Following the ratification of the peace deal between the FARC and the Colombian government on November 30, 2016, Marin and the rest of the FARC guerrillas have demobilized and begun the disarmament process.
The former negotiation leader was elected party leader at the FARC’s first party congress in August 2017.
After major frustrations with the peace process, the arrest of fellow FARC-commander and friend “Jesus Santrich,” and the alleged appearance of hooded men at his home, Marin disappeared again in August 2018.