The Primarch is the most important political figure on the planet Raimon. Jean-Luc Picard was the Federation's envoy to the death celebration of the Primarch when Picard was on the USS Stargazer.
In 2365 that Primarch's son, Sarlis Gaspadral was holding his death celebration when Picard was again asked to attend. Gaspardral was murdered and at that time, the next in line for the Primarch position was his daughter Lutina, but after confessing to the murder of her father, Raimon had to search for a new Primarch. (TNG comics: "Return to Raimon", "Murder, Most Foul")