[I Thessalonians 2:13-15] For this cause also thank we God without ceasing, because, when ye received the word of God which ye heard of us, ye received it not as the word of men, but as it is in truth, the word of God, which effectually worketh also in you that believe. For ye, brethren, became followers of the churches of God which in Judaea are in Christ Jesus: for ye also have suffered like things of your own countrymen, even as they have of the Jews: Who both killed the Lord Jesus, and their own prophets, and have persecuted us; and they please not God, and are contrary to all men:
Well....just to be sure, I included the surrounding verses as well.....but I haven't the foggiest as to what you're getting at. Where does this scripture says these Jews are of the Northern kingdom?
Try comparing some scripture with scripture.
Which is how one is suppose to interpet scripture, not run to Lexicons and Interliners. (1Cor.2:13)
It was the Jews who killed the Lord and Peter says it was the House of Israel (Acts.2:36), thus, those people who were from the Northern Kingdoms were called Jews.
And that was the title that was put over the Lord's head, King of the Jews, and that was who He asked His Father to forgive, those who crucified Him, the Jews, from both Houses.