In comparing the genealogies of Christ in the Gospels of Luke and Matthew, notable discrepancies arise. The key distinctions are as follows: 1) Matthew identifies Jacob as Joseph's father (Matt. 1:16), whereas Luke names Eli (Luke 3:23). 2) The lineage from Salathiel to Zerubbabel differs; Matthew claims Salathiel is Jechoniah's son (Matt. 1:12), while Luke labels him Neriah’s son (Luke 3:27). Additionally, according to Matthew, Zerubbabel's son is Abiud (Matt. 1:13) while Luke names him Risaiah (Luke 3:27). 3) Joseph’s lineage is established through David’s line via Solomon in Matthew (Matt. 1:6-7), but through Nathan in Luke (Luke 3:31). 4) The names listed from David to Salathiel (Matt. 1:7-12, Luke 3:31-27) and from Zerubbabel to Joseph (Matt. 1:13-16, Luke 3:27-23) differ, and the total counts vary between the two accounts.
Several interpretations have been proposed to clarify these discrepancies: 1) One view is that Matthew presents the genealogy of Joseph, while Luke accounts for that of Mary, as both hail from David but through different ancestry. However, this is contradicted by Luke's explicit assertion that he is also outlining Joseph’s genealogy (v. 23), and genealogical records from the female side were not customarily maintained, despite Mary's descent from David. 2) Another theory suggests that the individuals listed might actually be the same people with varying names, in accordance with Jewish tradition where one individual might possess multiple names. However, this does not align with the fact that the genealogies distinctly diverge from David through Solomon and Nathan, who are indeed two separate individuals, nor does it reconcile the differing total counts. 3) A more plausible explanation is rooted in the law of levirate marriage, which mandated that a brother or closest male relative of a deceased man without offspring would marry his widow to perpetuate the family line (see note on Matt. 1:12). The offspring in such cases had dual paternity: one by nature and one by law. Thus, Matthew describes Salathiel as the legal son of Jechoniah, the childless man, while Luke refers to him as Neriah’s son, who continued the lineage of the childless Jechoniah.
Zerubbabel, adopted by Salathiel, had sons named Abiud and Risaiah; Matthew follows the lineage through Abiud while Luke traces it through Risaiah. There is a clear distinction in Matthew's line connecting to David via Solomon and Luke's via Nathan. Consequently, these genealogies lead back to Jacob and Eli, both identified as fathers of Joseph: Eli, son of Matthat, died without children, and Jacob, his nearest relative, restored the lineage through his widow and fathered Joseph. Thus, Joseph is considered the son of Jacob by genealogy and Eli by legal standing. This exploration of the genealogical differences traces back to Julius Africanus from the second century, who received this account from relatives of the Blessed Virgin (Euseb. Church Hist. 1, 7). This interpretation has gained acceptance among many Church fathers and scholars. There are also instances where this law of levirate marriage likely applied during periods when the Davidic lineage faced challenges, notably during Babylonian captivity and prior to Christ’s arrival, when the royal line of David ceased to reign in Jerusalem.