The oldest son of Israel was Reuben. But since he dishonored his father by sleeping with one of his father's concubines, his birthright was given to the sons of his brother Joseph. For this reason, Reuben is not listed in the genealogy as the firstborn son.
References for 1 Chronicles 5:1
It was the descendants of Judah that became the most powerful tribe and provided a ruler for the nation, but the birthright belonged to Joseph.
References for 1 Chronicles 5:2
The sons of Reuben, the oldest son of Israel, were Hanoch, Pallu, Hezron, and Carmi.
The descendants of Joel were Shemaiah, Gog, Shimei,
Micah, Reaiah, Baal,
and Beerah. Beerah was the leader of the Reubenites when they were taken into captivity by King Tiglath-pileser of Assyria.
References for 1 Chronicles 5:6
Beerah's relatives are listed in their genealogy by their clans: Jeiel (the leader), Zechariah,
and Bela son of Azaz, son of Shema, son of Joel. These Reubenites lived in the area that stretches from Aroer to Nebo and Baal-meon.
And since they had so many cattle in the land of Gilead, they spread eastward toward the edge of the desert that stretches to the Euphrates River.
During the reign of Saul, the Reubenites defeated the Hagrites in battle. Then they moved into the Hagrite settlements all along the eastern edge of Gilead.
Across from the Reubenites in the land of Bashan lived the descendants of Gad, who were spread as far east as Salecah.
Joel was the leader in the land of Bashan, and Shapham was second-in-command, along with Janai and Shaphat.
Their relatives, the leaders of seven other clans, were Michael, Meshullam, Sheba, Jorai, Jacan, Zia, and Eber.
These were all descendants of Abihail son of Huri, son of Jaroah, son of Gilead, son of Michael, son of Jeshishai, son of Jahdo, son of Buz.
Ahi son of Abdiel, son of Guni, was the leader of their clans.
The Gadites lived in the land of Gilead, in Bashan and its villages, and throughout the Sharon Plain.
All of these were listed in the genealogical records during the days of King Jotham of Judah and King Jeroboam of Israel.
There were 44,760 skilled warriors in the armies of Reuben, Gad, and the half-tribe of Manasseh. They were all skilled in combat and armed with shields, swords, and bows.
They waged war against the Hagrites, the Jeturites, the Naphishites, and the Nodabites.
They cried out to God during the battle, and he answered their prayer because they trusted in him. So the Hagrites and all their allies were defeated.
The plunder taken from the Hagrites included 50,000 camels, 250,000 sheep, 2,000 donkeys, and 100,000 captives.
Many of the Hagrites were killed in the battle because God was fighting against them. So they lived in their land until they were taken away into exile.
The half-tribe of Manasseh spread through the land from Bashan to Baal-hermon, Senir, and Mount Hermon. They were very numerous.
These were the leaders of their clans: Epher, Ishi, Eliel, Azriel, Jeremiah, Hodaviah, and Jahdiel. Each of these men had a great reputation as a warrior and leader.
But they were unfaithful and violated their covenant with the God of their ancestors. They worshiped the gods of the nations that God had destroyed.
So the God of Israel caused King Pul of Assyria (also known as Tiglath-pileser) to invade the land and lead away the people of Reuben, Gad, and the half-tribe of Manasseh as captives. The Assyrians exiled them to Halah, Habor, Hara, and the Gozan River, where they remain to this day.