Alejo (1635 - 1660) was a Chilean mestizo, who fought in the Arauco War. He was the son of the Mapuche cacique Curivilú and the Spanish Isabel de Vivar y Castro who was captured during a Mapuche raid. Isabel and Alejo were rescued five years later and rejoined the Spanish society. Alejo enlisted the Spanish army, but the system of castas prevented his promotion. As a result, he deserted from the Spanish army and joined the Mapuches, being appointed toqui. Instructed in Spanish military strategy, he posed a serious threat to his former masters, but he died in a crime of passion: after he had sex with a captured Spanish woman his two wives murdered him.

Alejandro Vivar, Isabel's father, was a Spanish soldier in the Captaincy General of Chile during the Arauco War against the Mapuches. He led an incursion into Mapuche territory and was ambushed by them. Isabel was captured and engaged to the cacique Curivilú. She had a son with him, known as "Alejandro de Vivar" by the Spanish and "Ñancú" by the Mapuche; but he used the diminutive form of the name "Alejo" instead.

Alejo Peyret (in French Alexis Pierre Louis Edouard Peyret; December 11, 1826 - August 27, 1902) was a French-born Argentine writer, agronomist, colonial administrator, and historian. He was a prominent figure in the history of Entre Ríos Province.

Peyret was born in Serres Castet, Canton Morlaàs, in the department of Basses-Pyrénées, today Pyrénées-Atlantiques,, the son of Alexis Agustin Peyret and Cecile Angelique Vignancour. He entered the Royal College of Pau at the age of ten. In 1844, at the age of eighteen, he earned a bachelor's degree in science and letters. He avoided compulsory military service by hiring a paid substitute to serve in his place . He went on to study law at the Collège de France, where his professors included the philosopher Edgar Quinet and the historian Jules Michelet. He became involved with political radicalism, writing editorials in support of republicanism, democracy, anticlericalism, and socialism, and of the Revolutions of 1848 in particular. He was tried for his activities, but acquitted of wrongdoing .