God changed Jacob's name to Israel. From Israel's 12 sons came the 12 tribes of Israel e.g. from Reuben came the Reubenites, from Levi came the Levites, from Benjamin came the Benjamites, and from Judah came the Jews. See Children of Jacob
An absolutely vital element of correctly understanding Bible Prophecy is that while all Jews are Israelites, not all Israelites are Jews (just like, for example, all Texans are Americans, but not all Americans are Texans). Only the descendants of Judah are Jews.
The Scepter To Judah
"The scepter will not depart from Judah, nor the ruler's staff from between his feet, until He comes to Whom it belongs, and the obedience of the nations is His." (Genesis 49:10)
Jesus Christ, The Savior, was a physical descendant of Judah (Matthew 1:1-17, Luke 3:23-38). See The Chosen People
The Birthright To Joseph's Sons - Ephraim and Manasseh
Just before he was about to die, Jacob/Israel called his son Joseph (see Coat Of Many Colors), father of one of the 12 tribes, to give him the blessing - in effect, the birthright. Joseph brought his two sons, Ephraim and Manasseh with him, and the birthright was given directly to them -
"Some time later Joseph was told, "Your father is ill." So he took his two sons Manasseh and Ephraim along with him. When Jacob was told, "Your son Joseph has come to you," Israel rallied his strength and sat up on the bed. Jacob said to Joseph, "God Almighty appeared to me at Luz in the land of Canaan, and there He blessed me and said to me, "I am going to make you fruitful and will increase your numbers. I will make you a community of peoples, and I will give this land as an everlasting possession to your descendants after you." [see Stairway To Heaven] "Now then, your two sons born to you in Egypt before I came to you here will be reckoned as mine; Ephraim and Manasseh will be mine, just as Reuben and Simeon are mine." (Genesis 48:1-5)
"Then he blessed Joseph and said, "May the God before Whom my fathers Abraham and Isaac walked, The God Who has been my shepherd all my life to this day, the Angel who has delivered me from all harm - may He bless these boys. May they be called by my name and the names of my fathers Abraham and Isaac, and may they increase greatly upon the earth." (Genesis 48:15-16)
In our time, Jews are the most easily identified Israelites. They returned from the Babylonian exile, and their descendants form the Jewish people today.
On the other hand, the descendants of Joseph, who were conquered and taken away by the Assyrians, never returned. They are part of what are today popularly known as "The Lost Ten Tribes" of Israel - not only were they lost to the world, they eventually became lost to themselves. And yet, they received the birthright promises, great national wealth and power, and end-time prophecy speaks even more of them than it does about the Jewish people.
Manasseh was prophesied to become "a great nation," while Ephraim was prophesied to become "a great commonwealth of nations" - both of which would exist in our time as political and military allies of Judah.
So, who are they?
There has been much speculation regarding their identity, but there is one theory that fits the prophecy with amazing perfection -
At the end of the First World War, Britain ("a great commonwealth of nations") took control of the land of Israel after the fall of the Ottoman empire that then held it. The British mandate continued until after the Second World War, when in 1948 they handed it over to the Jewish people who declared the modern state of Israel. Since 1948, the United States ("a great nation") has been the foremost supplier and defender of Israel. The modern state of Israel would have not come into being without the British, and would not have survived to this day without the Americans - two ancient brothers who helped another ancient brother get re-settled in the old homeland.
Are modern-day Britain/Canada/Australia/New Zealand/others and the United States really the descendants of Ephraim and Manasseh as some think? That question will be clearly answered by world events in the years just ahead.
Fact Finder: Were Manasseh and Ephraim, through Joseph, to possess great material wealth on the earth?