You have the two geneologies mixed up. Descended from Nathan is thru the line of Mary not Joseph.
That is not possible. Mary could not give Jesus the throne of David by inheritance. Only Joseph could.
Eusebius, 5th century, told the Church why the Jewish law gave the genealogies only to Jesus, through Joseph:
" Eusebius, chapter 7:
Chapter 7. The Alleged Discrepancy in the Gospels in regard to the Genealogy of Christ.
1. Matthew and Luke in their gospels have given us the genealogy of Christ differently, and many suppose that they are at variance with one another. Since as a consequence every believer, in ignorance of the truth, has been zealous to invent some explanation which shall harmonize the two passages, permit us to subjoin the account of the matter which has come down to us, and which is given by Africanus, who was mentioned by us just above, in his epistle to Aristides, where he discusses the harmony of the gospel genealogies. After refuting the opinions of others as forced and deceptive, he give the account which he had received from tradition in these words:
2. For whereas the names of the generations were reckoned in Israel either according to nature or according to law—according to nature by the succession of legitimate offspring, and according to law whenever another raised up a child to the name of a brother dying childless; for because a clear hope of resurrection was not yet given they had a representation of the future promise by a kind of mortal resurrection, in order that the name of the one deceased might be perpetuated—
3. whereas then some of those who are inserted in this genealogical table succeeded by natural descent, the son to the father, while others, though born of one father, were ascribed by name to another, mention was made of both of those who were progenitors in fact and of those who were so only in name.
4. Thus neither of the gospels is in error, for one reckons by nature, the other by law. For the line of descent from Solomon and that from Nathan were so involved, the one with the other, by the raising up of children to the childless and by second marriages, that the same persons are justly considered to belong at one time to one, at another time to another; that is, at one time to the reputed fathers, at another to the actual fathers. So that both these accounts are strictly true and come down to Joseph with considerable intricacy indeed, yet quite accurately.
5. But in order that what I have said may be made clear I shall explain the interchange of the generations. If we reckon the generations from David through Solomon, the third from the end is found to be Matthan, who begot Jacob the father of Joseph. But if, with Luke, we reckon them from Nathan the son of David, in like manner the third from the end is Melchi, whose son Eli was the father of Joseph. For Joseph was the son of Eli, the son of Melchi.
6. Joseph therefore being the object proposed to us, it must be shown how it is that each is recorded to be his father, both Jacob, who derived his descent from Solomon, and Eli, who derived his from Nathan; first how it is that these two, Jacob and Eli, were brothers, and then how it is that their fathers, Matthan and Melchi, although of different families, are declared to be grandfathers of Joseph.
7. Matthan and Melchi having married in succession the same woman, begot children who were uterine brothers, for the law did not prohibit a widow, whether such by divorce or by the death of her husband, from marrying another.
8. By Estha then (for this was the woman's name according to tradition) Matthan, a descendant of Solomon, first begot Jacob. And when Matthan was dead, Melchi, who traced his descent back to Nathan, being of the same tribe but of another family, married her as before said, and begot a son Eli.
9. Thus we shall find the two, Jacob and Eli, although belonging to different families, yet brethren by the same mother. Of these the one, Jacob, when his brother Eli had died childless, took the latter's wife and begot by her a son Joseph, his own son by nature and in accordance with reason. Wherefore also it is written: 'Jacob begot Joseph.' Matthew 1:6 But according to law he was the son of Eli, for Jacob, being the brother of the latter, raised up seed to him.
10. Hence the genealogy traced through him will not be rendered void, which the evangelist Matthew in his enumeration gives thus: 'Jacob begot Joseph.' But Luke, on the other hand, says: 'Who was the son, as was supposed' (for this he also adds), 'of Joseph, the son of Eli, the son of Melchi'; for he could not more clearly express the generation according to law. And the expression 'he begot' he has omitted in his genealogical table up to the end, tracing the genealogy back to Adam the son of God. This interpretation is neither incapable of proof nor is it an idle conjecture. "