Prophecy tells us that in the last days a servant of the Lord will reunite these two Kingdoms. This "Davidic Servant" will be a descendent of Judah and King David through the lineage of Jesse (The Kingdom of Judah) and he is a descendent of Joseph as well. (The Kingdom of Israel)
Isaiah 11 speaks of the servant of the Lord who is of mixed lineage. Joseph Smith was asked a question about this servant who is referred to as the root of Jesse and below you can read his response:
We have already established the fact that Joseph Smith holds the keys of the kIngdom in the last days along with the Keys of the Priesthood and the Keys of the gathering of Israel.
Now lets look closely at this prophesy about Joseph Smith in Isaiah 11. Please notice that the Lord sets his hand again the second time to recover the remnant of his people!
"And in that day there shall be a root of Jesse, which shall stand for an ensign of the people; to it shall the Gentiles seek: and his rest shall be glorious. And it shall come to pass in that day, that the Lord shall set his hand again the second time to recover the remnant of his people..."
In Isaiah, the Lord often refers to his Servant as his "Arm" and "Hand"....hense another translation of this scripture would read thusly:
"the Lord shall set his Servant again the second time to recover the remnant of his people..."
Again, we have another witness that the Marvelous Work is separate and distinct from the restoration of the church.
Gods servant attempted to gather Israel and redeem Zion during his first commission in the second watch but failed because of the wickedness of the gentile nation and the blindness upon modern Israel. But God will set his Servant again, the second time to recover hi people in the second commission during the third watch.