Sorry, my bad. To clear up - JH Allen in "Judah's Scepter and Joseph's Birthright" makes the claim that Jeremiah was the father-in-law of Jehoahaz, who was the grandfather (? trying to remember the book) of Zedekiah, which would make these "king's daughters" his (Jeremiah's) great-granddaughters. I find that improbable, considering Jeremiah 16:2. And considering that the two Jeremiahs - there are two in scripture - were from entirely different hometowns - one from Libnah (2 Kings 23:31) and one from Anathoth (Jer 1:1), that makes it even more unlikely that they were one and the same.
These daughters would be of Judah and not daughters of the House of Israel who had already been sent into captivity to the Assyrian king.
Right, which is one of the reasons that British Israelism loses me. They claim that the house of Israel, dispersed among the nations, has given birth to Britain, Scotland, Ireland, America, etc, and also that the "true" line of Judah has been maintained through the British monarchy. They base this claim on the "overturn, overturn, overturn" prophecy of Ezekiel 21:27, which seems more than a stretch to me, for various reasons.