The Minmatar society is very much based on tribal society. There are seven major tribes or clans, Sebiestor, Krusual, Brutor, Vherokior, Nefantar, Thukker and Starkmanir.
Of the seven clans, four make up the Minmatar Republic, Sebiestor, Krusual, Brutor and Vherokior. The Starkmanir tribe was almost totally destroyed by the Amarrians after a crushed rebellion four centuries ago, only a handful remain as slaves within the Amarr Empire. The Nefantars collaborated with the Amarrians during the latter control of the Minmatars. They were driven out alongside the Amarrians during the Minmatar Rebellion and today make up what's commonly known as the Ammatars. Lastly, the Thukkers are scattered throughout the world of EVE, their tribal bindings are very loose and many of them don't even consider themselves to be a part of a tribe any longer. These people have rejected many of the strongest traditions of the Minmatars, such as the tattooing process.
Here is a brief description of three of the seven tribes. The Amarrians gave each tribe a nickname, meant to be derogatory, but which the tribes embraced as being complimentary of their respective talents and uniqueness.
Nick: The Sinister
Tribe leader: Karin Midular
The Sebiestors are of slight build, but are lithe and often graceful. Pale, taut skin and thin frame is the norm and these looks lead many to belief they suffer from constant malnutrition and sickness. The Sebiestors favor simple tattoo forms - straight lines and clean patterns, but flowing, symbolic signs are not unheard of.
The Sebiestor tribe hails from the inhospitable steppes of the Mikramurka continent in the northern artic region on Matar. The Sebiestors are the most technically inclined of the Minmatar tribes and were at the forefront in the tentative space exploration program the Minmatars were undertaking just before the Amarrians arrived. Today, most of the Minmatar ships and stations are engineered by Sebiestors.
Nick: The Fierce
Tribe leader: Wkumi Pol
The Brutors are a swarthy people originating from the island-ridden southern hemisphere of Matar. They are a bit larger and burlier than the other tribes, and as they favor physical prowess over anything else they can be frightening to face in the flesh.
The Brutor tribe and the Starkmanir tribe were once one and the same, living in the vast Eyniletti-plains. Some thousands of years ago one of the sub-clans of this tribe traversed the Mioar-strait and started settling the islands in the Mioar archipelago, moving ever more southwards. In the end, this sub-clan lost contact with their head tribe and the Brutor tribe came into existence. The Amarrians enslaved the Brutors in droves; due to their physical strength the Brutors were ideal for manual labor. A considerable portion of the tribe is still enslaved within the Amarr Empire.
Nick: The Crafty
Tribe leader: Tenerhaddi Dykon
The Krusuals are tall, with brown skin. They keep their heads shaved at the sides, with only a narrow hairline running from their forehead to the back of their heads. The Krusual tribe uses flowing, often geometric tattoo motifs, seldom cluttered, always orderly and pleasing the eye.
The Krusual tribe initially inhabited the mountainous region of the upper Tronhadar-valley on Matar. The other tribes regarded the Krusuals as the most barbaric of them all, but that stemmed more from a lack of knowledge about the intricate culture of the secluded Krusuals rather than being an actual fact. The Amarrians had real difficulties subduing the Krusuals during their conquest of the Minmatars and the unruly Krusuals in their mountain bases were always a thorn in the Amarr side.
The large, fertile plains of Matar, home planet of the Minmatars, with endless herds of hoofed animals, proved ideal for a nomadic lifestyle. The fabulous conditions on Matar coupled with more than enough space meant there was less incentive to struggle to keep up the technology level after the closure of the EVE gate. For ages the Minmatars roamed this paradise, slowly divided by time and distance into numerous tribes.
The tribal community was ideally suited for nomads, but remarkably the Minmatars kept their strong tribal ties after urbanization began, even if some of its more strict aspects have declined in recent times, such as the stringent caste system and (for some of the tribes) acreage serfdom for farmers and workers. To this day, Minmatars identify themselves first and foremost through their clan.
The Minmatar tribes evolved their own traditions over time, but limited communications between them ensured a few basic similarities in their social structure. One of these is the pyramid structure of the tribe: each tribe has a number of family clans, which are then further divided into sub-clans based on occupation, geographical location and other traits (this is different between the tribes even if the overall structure is the same). Each of the seven major tribes has a tribal leader; this person serves pretty much the same position as a president or a head of state for the tribes. The authority of the tribe leader is unquestioned within the tribe, but he has little or no power outside his tribe. The clan structure is both one of the main strengths and main weaknesses of the Minmatars. On the one hand the strong tribal bonds have kept the Minmatars pure in their cultural heritage, but on the other hand it makes them politically weak and vulnerable versus the other empires.