'Eldest' in the Bible

And the three eldest sons of Jesse had gone after Saul to the battle: and the names of his three sons that went to the battle were Eliab the first-born, and next unto him Abinadab, and the third Shammah.

And David was the youngest; and the three eldest followed Saul.

And Eliab his eldest brother heard when he spake unto the men; and Eliab's anger was kindled against David, and he said, Why art thou come down? and with whom hast thou left those few sheep in the wilderness? I know thy pride, and the naughtiness of thy heart; for thou art come down that thou mightest see the battle.