'Firstborn Son' in the Bible

"If a man has two wives, [and] the one [is] loved and the [other] one [is] disliked and the one loved and the one that is disliked have borne for him sons, if it happens [that] the firstborn son {belongs to the one that is disliked},

[nevertheless] {it will be the case that} on the day of bestowing his inheritance upon his sons, he will not be allowed to treat as [the] firstborn son the son of the beloved [wife] {in preference to} the son of the disliked [wife], [who is] the firstborn [son].

But he shall acknowledge the firstborn son of the disliked [wife] {by giving} him a double portion of {all that he has}, for he [is] the firstfruit of his vigor; to him [is] the legal claim of the birthright.

The name of his firstborn son [was] Joel, and the name of his second son [was] Abijah. [They were] judges in Beersheba.

He took his firstborn son who was to become king in his place and offered him [as] a burnt offering on the wall. Great wrath came upon Israel, and they withdrew from him and returned to the land.

And his firstborn son [was] Abdon, then Zur, Kish, Baal, Nadab,

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

And she gave birth to her firstborn son, and wrapped him in strips of cloth and laid him in a manger, because there was no place for them in the inn.