'Oldest' in the Bible

The three oldest sons of Jesse followed Saul into battle. The names of his three sons who went to the battle were his firstborn Eliab, Abinadab, his second son, and Shammah, the third.

David was the youngest, while the three oldest had followed Saul.

Eliab his oldest brother heard him talking to the men. Eliab was angry with David and said, "Why did you come down here? And who did you leave those few sheep with in the wilderness? I know your insolence and wicked intentions. You came down just to see the battle!"