The First Families of Rigel were a group that existed on the planet Rigel IV in the Rigel system.
They were noted as being a consortium of powerful family groups that existed on the Rigelian world. The members of these elite groups were virtually in control of their home world and had a great deal of money at their disposal making them influential. Individuals from the First Families possessed their own private ships and had no need to go through transporter, sensor or baggage scans. The First Families also held a number of secrets from the United Federation of Planets which included stored samples of Rigelian fever.
Crofter Thamnos was a member of the First Families of Rigel. (ST - The Lost Era novel: Catalyst of Sorrows)