Reuben was the first child of Jacob and Leah, and the founder of the tribe of Reuben. When the Bible lists the names of Jacob's 12 sons, Reuben's is listed first. But Reuben lost the privileges that traditionally were given to first-born sons because he had an affair with Bilhah, who was his father's concubine (Genesis 35:22). Reuben, however, is noted for some good things.
He intervened with his brothers to spare Joseph's life in Genesis 37:21-30.
He also offered his own sons as surety for Benjamin's safety in Genesis 42:37. The Bible has other details about Reuben and the tribe of Reuben: Reuben followed his father, Jacob, as the family traveled from Padan Aram to Canaan, and then later to Egypt.
His descendants took part in Korah's revolt against Moses as described in Numbers 16:1-3. And the loss of life from that rebellion helps to explain why the population of the Tribe of Reuben dropped from 46,500, to 43,730 during the time between the two censuses that were taken in Numbers 1:21 and Numbers 26:7.
In Revelation 7:1-8, the tribe of Reuben is listed among the tribes who are promised the Seal of God for 12,000 of their members.
The name Reuben means "see a son."