In Matthew's genealogy of Jesus, he records the names of both of the sons of Judah and Tamar: Perez and Zerah, who were twins. Zerah is not a direct ancestor of Jesus, since the line goes through Perez. Yet, Matthew doesn't record the names of any other sons who were not part of the line he traces - not even Esau who like Zerah was a twin. Jeconiah's brothers are briefly mentioned in 1:11, but not by name. Why would Matthew include Zerah's name, then, into the genealogy?
Judah was the father of Peretz, but Tamar was known as the "mother of Peretz and Zerah" and the emphasis is on the maternal side in this verse, as in verses 5 and 7 referring respectively to the sons of the matriarchs Rahav, Ruth and Bat-Sheva.
See also the wording of the genealogy in Chronicles I 2:4 where the twins are mentioned as the sons of Tamar.
See also Genesis 28:5, "Rebekah, mother of Jacob and Esau".
Note that the Book of Genesis describes the physical birth of the two twins, Perez and Zerah, in great detail. (Genesis 38:27-30) By mentioning the two together, Matthew brings to mind their birth and consequentially the circumstances of their birth; namely, that they were a result of Judah's abominable fornication.
Now, you might object that, if Matthew's intended to highlight Judah's sin of fornication, it would have been sufficient for Matthew to omit Zerah's name since he mentions Tamar. But I claim that it was wise for Matthew to include the name rather than to omit it. Why? We know he was writing to a Jewish audience who were probably familiar with the Book of Genesis and the other scriptures, yet it would be rash to assume that every Jew had a perfect memory of every scriptural detail. Perhaps a good portion had heard the story of Judah having twins through fornication and the dispute over which of the two would be "firstborn," but maybe did not remember the name of the woman. By mentioning the two twins, Matthew makes it easier for his audience to recall the story and thus to recall Judah's sin.
Notice that, in his genealogy, Matthew also alludes to David's sin of adultery. With these examples, Matthew illustrates that, although Christ was perfect, his forefathers were not.
Why would Matthew want to illustrate this? We can only speculate. Here are a few possibilities:
To show the abundant sin in the world and thus the need for Christ to come as a redeemer.
To show that we are not doomed to follow in the sinful footsteps of our forefathers. For instance, although I myself am a Gentile and probably have pagan ancestors, I do not need to imitate their idolatry.
To show that the Jewish people were not spotless, thus preparing Jews to renounce any Jewish pride which might hinder them from accepting Christ's universal religion in which embraces Jews and Gentiles as equal. "There is neither Jew or Gentile" writes Paul.
Could it have to do with the fact that the Zerahite line spawned Prince Eochaidh (later crowned as King Heremon) of Ireland, who married Tea Tephi, King Zedekiah's daughter? Tea Tephi was apparently brought to Ireland by the prophet Jeremiah along with the "Stone of Destiny". The Davidic Royal line then transfers to Scotland (along with the coronation "Stone of Destiny") and then ultimately to England. Hence, fulfilling God's promise to David that he would never lack a man on the throne, as well as His promise to Judah that "the sceptre would not depart from him until Shiloh (Messiah) comes". Could be why the Holy Spirit had Matthew include Zerah in his genealogy.
Matthew includes both Zerah and his mother Tamar:
and Judah the father of Perez and Zerah by Tamar... (Matthew 1:3) [ESV]
This recalls the story of Judah's first three sons, Er, Onan, and Shelah. After Er died childless, Onan should have produced an heir for Er but he refused and he too died childless. When Judah refused to give Shelah to Tamar, she pretended to be a prostitute with whom Judah produced two more sons. Thus, there are two ways to understand the genealogy from Judah to the next generation:
Judah Judah Er by Shua Er's son by Tamar Zerah and Perez by Tamar
The reference to Zerah serves as a reminder Er's generation is missing
1 and invites the reader to consider the parallels within all of the genealogic sequences:
Actual Birth Sequences: Recorded Genealogy: Isaac Judah Isaac Judah Esau (Rebecca) Zerah (Tamar) [Esau - omitted] [Zerah - omitted] Jacob (Rebecca) Perez (Tamar) Jacob Perez
Like Esau Er is missing from the record. Moreover, since Judah fathered twins, Zerah and Perez were his 4th and 5th sons. While Judah thought Tamar was a prostitute she returned the amount Judah paid. In so doing effectively became Judah's concubine. Consequently, Matthew's reckoning of David's genealogy goes from Judah who was Jacob's 4th son to Perez who was Judah's 5th son:
David's Genealogy Judah's sons Jacob's sons 1 Abraham 1 Er 1 Rueben 2 Isaac 2 Onan 2 Simeon 3 Jacob 3 Shelah 3 Levi 4 Judah 4 Zerah (Tamar) 4 Judah 5 Perez (Tamar) 5 Perez (Tamar) 5 Dan (Bilhah)
By including Zerah and Tamar, Matthew has presented three genealogic sequences which arrive at a 5th son from a mother who was not a wife of the father.
1. Omitting Er also may figure into Matthew's counting of 14 generations from Abraham to David and from David to the exile. If Er is counted, David can be omitted in the count from Abraham and only included in the count to the exile.
You have to look at world history from the time of Judah’s twins to the time of Jesus birth and align the “missing tribes of Israel” with what other peoples called them in those languages which normally correspond with the symbol Jacob gave to the sons during their blessings. Also, God has a way of keeping his promises that we can’t see unless we dig for the truth, the modern church has a way of omitting things but I’m glad it does because if you really want to seek out the truth of Jesus you will take the time to do it. Once you trace out world history with the prophecy of Jacob about his sons and 2 of his grandsons you’ll be amazed.
I can’t imagine why Matthew listed Zerah in the genealogy of Jesus Christ. For it is apparent he was not part of the genealogy. The first letter that Paul wrote to Timothy; 1 Timothy 1:3-7 As I urged you when I went into Macedonia — remain in Ephesus that you may charge some that they teach no other doctrine, 4 nor give heed to fables and endless genealogies, which cause disputes rather than godly edification which is in faith. 5 Now the purpose of the commandment is love from a pure heart, from a good conscience, and from sincere faith, 6 from which some, having strayed, have turned aside to idle talk, 7 desiring to be teachers of the law, understanding neither what they say nor the things which they affirm. NKJV we are told not to teach any other doctrine nor give heed to fables and endless genealogies. The stone of scone is more a fable than Mother Goose
One of several authors that discuss facts of Zerah's many descendants and kingdoms are presented in the link above. Or do you repose the scepter of Judah died out perhaps and God's word was voided? God will not be mocked! A man's ignorance is his own and likely in this case, Zerah's line, a secret for God's purposes.
I think it is actually self-evident that God made also his promise to Abraham and Sarah to be parents of nations through mostly Zerah whose finger was tied with scarlet thread (also the color of royalty) as Judah’s royal line.
Moreover, with good reason, people believe Jesus himself visited Wales where his wealthy uncle (who took charge of Jesus after his crucifixion) had a tin mine during those missing years before 30. There is considerable evidence this same uncle fled there with several of Jesus’s followers and family as well. And so on, there are multiple connections of this kind between Israel and other nations and most of these nations were founded by sons of Abraham or Zerah.