Leah became pregnant and gave birth to a son. She named him Reuben, for she said, "It is because the LORD has seen my misery. Surely my husband will love me now."
Reuben was the eldest son of Jacob and Leah, and by virtue of his being the first born, he should have been given preeminence over his brothers and a double portion of inheritence. Like his uncle Esau, however, he blew it, though for quite different reasons.
While Israel was living in that region, Reuben went in and slept with his father's concubine Bilhah, and Israel heard of it. (Genesis 35:22)
Though the immediate consequences of his actions aren't stated, it brought upon him his dying father's malediction.
"Reuben, you are my firstborn,
my might, the first sign of my strength,
excelling in honor, excelling in power.
Turbulent as the waters, you will no longer excel,
for you went up onto your father's bed,
onto my couch and defiled it.
There were redeemable qualities in Reuben, however. He showed kindness to Joseph, and saved his life when the other brothers plotted to kill him
"Come now, let's kill him and throw him into one of these cisterns and say that a ferocious animal devoured him. Then we'll see what comes of his dreams."
When Reuben heard this, he tried to rescue him from their hands. "Let's not take his life," he said. "Don't shed any blood. Throw him into this cistern here in the desert, but don't lay a hand on him." Reuben said this to rescue him from them and take him back to his father.
Again, it was Reuben who pledged his life and the life of his sons when Jacob was unwilling to let Benjamin go down into Egypt. After Jacob and his family went down into Egypt no further mention is made of Reuben beyond his father's dying declaration, though his legacy continued briefly through the tribe he founded: the Reubenites. After the Exodus, the Reubenites made a covenant with Moses to occupy an area of Gilead, east of The Jordan River and The Dead Sea. They suffered oppresion in the time of Jehu and were later taken into captivity by Tiglath-Plesar of Assyria where they, along with others of the Northern Kingdom, became one of the Lost Ten Tribes of Israel.