Who is Jeri Kingsolver from Citizen of the Galaxy and what is their importance?

Jeri Kingsolver is Thorby's adoptive nephew in the Free Traders, Jeri is the senior firecontrolman on the Sisu. Jeri is responsible for training Thorby as his replacement. Jeri has less patience with Thorby's unfamiliarity with Sisu customs than Captain Kraussa or Fritz.