Complex sentence: Out of court, however, they along with Edward Livingston, Jean Laffite, Pierre Laffite and others were actually colleagues in a clandestine group, referred to as the "association", that profiteered by illegally seizing Spanish property.
Split into simpler sentences: Out of court, however, they, along with Edward Livingston, Jean Laffite, Pierre Laffite and several others, were actually colleagues. They belonged to a clandestine group, referred to as the "association", that profited from illegally seized Spanish property.