Only partially.
The Genesis 35 and 48 prophecies to Jacob and Ephraim is specifically about their SEED in the sense of literal FLESH SEED.
Would they eventually begin to INCLUDE believing Gentiles in Christ? Yep! That's why Paul quoted from the Book of Hosea in Romans 9 also, which Hosea was written to the ten tribes of Israel of what God was getting ready to do to them for their falling away.
OK, the mystery... but most here won't like it:
God gave ten tribes to Jeroboam, who was born of the tribe of Ephraim. The tribe of Ephraim became the 'head' tribe over the ten northern tribes. Solomon had even appointed Jeroboam as a leader over the northern ten tribes even before God split the old kingdom in Solomon's day.
These verses point to God's plan for the 'seed' of Ephraim...
Deut 33:17
17 His glory is like the firstling of his bullock, and his horns are like the horns of unicorns: with them he shall push the people together to the ends of the earth: and they are the ten thousands of Ephraim, and they are the thousands of Manasseh.
KJV
Ephraim's seed was to become "a multitude of nations", and Manasseh's seed also was to become "great". Both were ordained to push the people together to the ends of the earth, put for their strong military power God would make of them. This was a prophecy continuing the one Jacob gave from God to them in Genesis 48. It was a continuation of God's promises to Abraham, that his seed would possess the gate of their enemies (Genesis 22:17). And because both of Joseph's sons were blessed together, they like Joseph represented the double-portion idea given to God's election.
Ps 60:7
7 Gilead is Mine, and Manasseh is Mine; Ephraim also is the strength of Mine head; Judah is My lawgiver;
KJV
Even though the ten tribes under Ephraim as head would be scattered by God, that prophecy above about them was still in effect. They would become a great number of seed in the world, Manasseh also, along with the rest of the ten tribes.
Ps 108:8
8 Gilead is Mine; Manasseh is Mine; Ephraim also is the strength of Mine head; Judah is My lawgiver;
KJV
Jer 31:9
9 They shall come with weeping, and with supplications will I lead them: I will cause them to walk by the rivers of waters in a straight way, wherein they shall not stumble: for I am a father to Israel, and Ephraim is my firstborn.
KJV
That idea of Ephraim being God's "firstborn" is about the idea of election. Ephraim became the inheritor of God's Birthright promises (originally given to Abraham, then to Isaac, then to Jacob, and then finally to Ephraim and Manasseh where God's Birthright still exists today). But the Birthright part of chief royal ruler went to the tribe of Judah (and is to remain with Judah until Jesus comes - see Genesis 49:10) ...
1 Chron 5:1-2
5 Now the sons of Reuben the firstborn of Israel, (for he was the firstborn; but, forasmuch as he defiled his father's bed, his birthright was given unto the sons of Joseph the son of Israel: and the genealogy is not to be reckoned after the birthright.
2 For Judah prevailed above his brethren, and of him came the chief ruler; but the birthright was Joseph's
KJV
That is not just talking about a fleshy birthright, but God's Birthright which is different. It is about God's promises first given through Abraham, and one of the main promises was the Promise by Faith, i.e, The Gospel of Jesus Christ (see Galatians 3). Other parts of the promises involve the best lands and resources (i.e., plenty of corn and wine), possessing the gate of thy enemies (i.e., great military power), and The Gospel of course, and a literal seed as many as the stars and sands of the sea.
Ezek 37:16
16 Moreover, thou son of man, take thee one stick, and write upon it, For Judah, and for the children of Israel his companions: then take another stick, and write upon it, For Joseph, the stick of Ephraim, and for all the house of Israel his companions:
KJV
As I've already shown elsewhere, the stick representing Joseph is in the hand of Ephraim, and the ten scattered tribes of Israel. They still exist today, just not in the holy land. But they still exist today because the above Ezekiel 37 prophecy is ONLY for the future at Christ's coming. That other stick, "For Judah", is about the "house of Judah", the JEWS today.
Historically what happened to the ten tribes when they were scattered out of the holy lands to Assyria and lands of the Medes, they became lost to themselves and to the world and to the Jews. Judah kept their heritage as part of Israel. But the ten tribes did not. God pretty much reveals all this through His prophet Hosea. God gave the ten tribes the full strength Baal worship they fell into. He scattered them for it, and they began to taken on other names from being among the Gentile nations. But God said He would lead them into the wilderness, and they would not find their way back. And there, He would one day speak softly to them, and take the names of Baali out of their mouths, and call Him "Ishi".
That actually happened to the ten tribes under Ephraim. They eventually left their captivity in Assyria and migrated mostly westward into Asia Minor and Europe. They would become the majority of the people of the western nations, and they brought their Baal idols with them. Each people in Asia Minor and Europe had their own idol worship names for their false gods. But once Jesus was rejected in Jerusalem, The Gospel began to be preached to them in the west, and they would become western Christian nations of history. And then from there, they would send out ambassadors to other nations, preaching The Gospel to them. The main difference from their Old Testament history and today is, most of them don't really know who they, not knowing their heritage as part of old Israel. But God knows.
And the reason why Apostle Paul quoted from Hosea in Romans 9 when speaking to Roman Gentile believers on Christ, is this. In Hosea, God called the ten tribes when they fell away as 'Lo ammi', meaning 'not My people'. Per Jeremiah 3, God gave the ten tribes a symbolic "bill of divorce" because of their falling to Baal worship. But then also per Hosea in final, God said He would have mercy upon a people that were not His people, and in the place where they were called 'Lo Ami' (meaning the ten tribes in rebellion), there He would call them 'My people', and they would call Him their GOD.
Hos 1:10
10 Yet the number of the children of Israel shall be as the sand of the sea, which cannot be measured nor numbered; and it shall come to pass, that in the place where it was said unto them, "Ye are not My people", there it shall be said unto them, "Ye are the sons of the living God."
KJV
Paul quoted that above in red to Roman Gentile believers in Romans 9. Thus the believing Gentile is joined... with believing Israel by his quoting that from Hosea, because Hosea was originally written to the ten tribe house of Israel. By Paul quoting that to believing Gentiles further showed that where he was and had preached The Gospel to mainly (i.e., Asia Minor and Europe), that... is where the majority of the scattered ten tribes were located, and to them The Gospel especially was sent (Matthew 15:24).
However, the Jews do not like this Bible prophecy nor how I showed it being fulfilled, with the western Christian nations representing the fulfillment of the "multitude of nations" prophecy to Ephraim, and that Manasseh his brother also would be "great". I can't help how those Jews feel, because like 1 Chronicles 5 shows, God's Birthright landed in final upon Joseph's two sons Ephraim and Manasseh, and that is by God's ordaining, not man's. So if the Jews don't like it, they can take it up with Him. As for the 'false Jews' who really, strongly, hate this teaching from God's Word, I could care less what they think, since they are mostly foreigners of the old Canaanite nations which Israel was not able to destroy, and thus crept in among Israel, especially among the tribe of Judah, and stole that title of Jew (thus the 'tares' of the parable of the tares of the field in Matthew 13).
