The throne came down through Solomon, but didn't the seed come down through his brother Nathan?Acts 2:30 Therefore being a prophet, and knowing that God had sworn with an oath to him, that of the fruit of his loins, according to the flesh, he would raise up Christ to sit on his throne;
(Promise to David: his house would be established forever & his throne would be established forever)
II Samuel 7:16 And thine house and thy kingdom shall be established for ever before thee: thy throne shall be established for ever.
I Kings 9:5 Then I will establish the throne of thy kingdom upon Israel for ever, as I promised to David thy father, saying, There shall not fail thee a man upon the throne of Israel.
(The promise that David's throne would be established forever, was to be through Solomon)
I Chronicles 22:9 Behold, a son shall be born to thee, who shall be a man of rest; and I will give him rest from all his enemies round about: for his name shall be Solomon, and I will give peace and quietness unto Israel in his days.
10 He shall build an house for my name; and he shall be my son, and I will be his father; and I will establish the throne of his kingdom over Israel for ever.
(It would be David's physical seed that the LORD would cause to sit on throne)
Ps 132:11 The LORD hath sworn in truth unto David; he will not turn from it; Of the fruit of thy body will I set upon thy throne.
(But then Coniah, David's royal seed down from Solomon, was promised that none of his seed [the continuation of the royal seed of David down from Solomon]) would ever sit upon the throne of David)
Jeremiah 22:24 As I live, saith the LORD, though Coniah the son of Jehoiakim king of Judah were the signet upon my right hand, yet would I pluck thee thence;
28 Is this man Coniah a despised broken idol? is he a vessel wherein is no pleasure? wherefore are they cast out, he and his seed, and are cast into a land which they know not?
29 O earth, earth, earth, hear the word of the LORD.
30 Thus saith the LORD, Write ye this man childless, a man that shall not prosper in his days: for no man of his seed shall prosper, sitting upon the throne of David, and ruling any more in Judah.
(How could the promise that the seed of David's house and David's throne would be established forever, when God stopped the royal seed at Coniah, from ever sitting on David's throne again? Only the virgin birth could bring this about. The promise of David's seed being established forever was kept by Mary being a direct descendant of David, not of the royal seed line through Solomon, but of the line of Nathan, one of the other sons of David and Bathsheba. Then secondly, the promise that David's throne would be established forever, was kept by Joseph being of the seed royal down through Solomon - the right of the throne belonged to Joseph by his royal lineage, given by Matthew - but no seed of Coniah, including Joseph and any of Joseph's seed could ever sit on David's throne - but since Jesus was not Joseph's seed, only Mary's, Jesus became Joseph's firstborn by right of adoption - and as Joseph's adopted firstborn, the right of the throne was given to Jesus, without violating the promise to Coniah. But since Jesus was Mary's son, and thereby of the seed of David through Nathan, both promises to David would still be kept - but only by the virgin birth of Jesus - nothing else could work and still keep the scriptures)
(Joseph's lineage down from David through Solomon, is given in Matthew 1, the royal line: Solomon, Roboam, Abia, Asa, Josaphat, down through Coniah [Jeconias].
However in Luke 3, the Davidic lineage of Mary, goes back through a different line, through Nathan, another son of David with Bathsheba. Joseph is mentioned in line 23, but it is mentioned that he is the son of Heli, this is not a contradiction, he could only be Joseph's father-in-law, Mary's father, since only the men are mentioned in that lineage, that it is Mary's father, mentioned as Joseph's father-in-law.)
Luke 3:31 Which was the son of Melea, which was the son of Menan, which was the son of Mattatha, which was the son of Nathan, which was the son of David,
(Nathan and Solomon are both sons of David and Bathsheba)
II Samuel 5:14 And these be the names of those that were born unto him in Jerusalem; Shammua, and Shobab, and Nathan, and Solomon,
(Only the virgin birth of Jesus by Mary, espoused to Joseph, could make all this work)