'First born' in the Bible

And Canaan begat Sidon his firstborn, and Heth,

These are their generations: The firstborn of Ishmael, Nebaioth; then Kedar, and Adbeel, and Mibsam,

The sons of Judah; Er, and Onan, and Shelah: which three were born unto him of the daughter of Shua the Canaanitess. And Er, the firstborn of Judah, was evil in the sight of the LORD; and he slew him.

And Jesse begat his firstborn Eliab, and Abinadab the second, and Shimea the third,

And the sons of Jerahmeel the firstborn of Hezron were, Ram the firstborn, and Bunah, and Oren, and Ozem, and Ahijah.

And the sons of Ram the firstborn of Jerahmeel were, Maaz, and Jamin, and Eker.

Now the sons of Caleb the brother of Jerahmeel were, Mesha his firstborn, who was the father of Ziph; and the sons of Mareshah the father of Hebron.

These were the sons of Caleb the son of Hur, the firstborn of Ephratah; Shobal the father of Kiriath-jearim,

Now these were the sons of David, who were born unto him in Hebron; the firstborn Amnon, of Ahinoam the Jezreelitess; the second Daniel, of Abigail the Carmelitess:

And the sons of Josiah were, the firstborn Johanan, the second Jehoiakim, the third Zedekiah, the fourth Shallum.

And Penuel the father of Gedor, and Ezer the father of Hushah. These are the sons of Hur, the firstborn of Ephrathah, the father of Bethlehem.

Now the sons of Reuben the firstborn of Israel, (for he was the firstborn; but, since he defiled his father's bed, his birthright was given unto the sons of Joseph the son of Israel: and the genealogy is not to be recorded according to the birthright.

The sons, I say, of Reuben the firstborn of Israel were, Hanoch, and Pallu, Hezron, and Carmi.

And the sons of Samuel; the firstborn Joel, and Abijah.

Now Benjamin begat Bela his firstborn, Ashbel the second, and Aharah the third,

And his firstborn son Abdon, and Zur, and Kish, and Baal, and Nadab,

And the sons of Eshek his brother were, Ulam his firstborn, Jeush the second, and Eliphelet the third.

And of the Shilonites; Asaiah the firstborn, and his sons.

And Mattithiah, one of the Levites, who was the firstborn of Shallum the Korahite, had the office of trust over the things that were baked in the pans.

And his firstborn son Abdon, then Zur, and Kish, and Baal, and Ner, and Nadab,

And the sons of Meshelemiah were, Zechariah the firstborn, Jediael the second, Zebadiah the third, Jathniel the fourth,

Moreover the sons of Obed-edom were, Shemaiah the firstborn, Jehozabad the second, Joah the third, and Sacar the fourth, and Nethanel the fifth,

Also Hosah, of the children of Merari, had sons; Shimri the chief, (for though he was not the firstborn, yet his father made him the chief;)