Barzillai was the name of several men. The best-known was a wealthy Gileadite of Rogelim who supported David and his army during Absalom’s rebellion. Other Barzillais included the father of Adriel and a man connected with a priestly family after the exile.
The Gileadite Barzillai supplied provisions to David, accompanied him across the Jordan after Absalom’s defeat, and declined David’s invitation to live in Jerusalem because of his advanced age. David later charged Solomon to show kindness to Barzillai’s sons.
Barzillai was about eighty years old when David returned to Jerusalem. A later priestly family could not prove its genealogy because its ancestor had married into the family of the Gileadite Barzillai and adopted that family name.