The Jomsvikings are at the elite level of the much larger organisation of Jomsborg.
Jomsborg is a worldwide organisation dedicated to recreating aspects of viking warrior culture in the modern age. It's 700+ members are divided culturally into five Storms, each led by a Storm commander. The members display a similar level of commitment to historical accuracy and steel weapon combat ability as the Jomsviking Brotherhood. The Jomsborg organisation banner is a red cross on black background, which is also official shield colors of every fighter. Jomsborg has a military command structure: Jarl - Storms - Styrsmen - Drengir (warriors) and household (non-combatants).
One shield, One Brotherhood!