The Chronicle of Alfonso XI [es], written in the 1370s, hints at the existence of the Brotherhood by the time of the Castillian conquest of Álava in 1200.
[5] It is likely that the Brotherhood originated in response to the growing power of towns in Álava, which threatened the interests of the rural nobility.
Most high-ranking members of the Brotherhood belonged to notable Castillian families, such as the houses of Lara, Haro, Cameros and Salcedo.
[9] In February 1332 an arbitration ruling was issued regarding the ownership of 45 hamlets disputed by the Brotherhood and the towns of Vitoria and Salvatierra.
[10] By the time of the Castillian conquest in 1200, seven settlements in Álava had been given town status: Salinas de Añana, Laguardia, Vitoria, Antoñana, Bernedo, Arganzón and Labraza.