what about a man descended from Solomon? would there still be a need of virgin birth?
Yes, Solomon no longer had the promise of a Messiah, only David did.
1 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.
1 Kings 9:6 But if ye shall at all turn from following me, ye or your children, and will not keep my commandments and my statutes which I have set before you, but go and serve other gods, and worship them:
1 Kings 9:7 Then will I cut off Israel out of the land which I have given them; and this house, which I have hallowed for my name, will I cast out of my sight; and Israel shall be a proverb and a byword among all people:
And that’s what happened:
1 Kings 11:4 For it came to pass, when Solomon was old, that his wives turned away his heart after other gods: and his heart was not perfect with the LORD his God, as was the heart of David his father.
Judah and Israel split, God let it go on a while, then finally smashed them both and they’ve been gone ever since.
Only David has a valid promise for Messiah, and it went to Jesus so David would never fail to have his son on the throne. That’s why a virgin birth was needed, so God could keep His promise.