Three years after Jax Teller met his maker in the dramatic Sons series finale, viewers were introduced to the Santo Padre charter of the Mayans M.C., including new prospect and series star EZ (JD Pardo).
SAMCRO's alliance with the Galindo cartel started in season four, with Clay (Ron Perlman) moving the Sons into the drug business as a way to keep control of the club, and his gun business afloat.
Knowing the Sons should never have gotten into drugs, one of the last things Jax (Charlie Hunnam) does before his death is give that side of the business, as well as the Diosa, to the Mayans.
Though it is likely that the Santo Padre charter and the Galindo cartel might have had a business relationship prior to that, due to their closeness to the border, it's not yet certain. The cartel and Oakland Mayans charter president Marcus Alvarez (Emilio Rivera) first began to work together in the series finale, meaning we can attribute their close relationship at the beginning of the spinoff series to that emblematic moment.
Alvarez also takes on a prominent role in Mayans M.C., helping out with the initial unrest within the businesses between the Mayans and the cartel, now under the leadership of Miguel (Danny Pino), the son of the Galindo cartel's leader, who was often talked about on Sons but never seen.
Viewers can also thank the original run of Sons of Anarchy for giving us the iconic moment featuring the San Bernardino charter of the motorcycle club.
At the beginning of Sons, the club and the Mayans were on opposite sides. The clubs craved blood in their battle for power and did not consider themselves allies in the least at the beginning. Throughout the series, the relationship among the members of the club turned for the better as Alvarez and Jax became allies to face common enemies, or find mutual ground, largely thanks to their common friend Nero (Jimmy Smits).
The beginning of Sons of Anarchy sees the Mayans break into and destroy one of the Sons warehouses. In the Mayans M.C. premiere, the TV universe offers insight into how much their relationship has changed when the San Bernardino charter of the Sons comes to the rescue of the Mayans, who are outnumbered in a fight against a Samoan group.