Judah
Judah was the fourth of Jacob's twelve sons. He was also the fourth of six sons he produced through Leah. He was born when Jacob was roughly 88 years old.
Judah's name in Hebrew means "praise."
It was Judah who urged his nine brothers to sell their then youngest brother Joseph into slavery instead of murdering him (Genesis 37:26 - 27). The brothers were, in part, jealous of the attention Joseph was receiving from the father. This was especially true after he received a "coat of many colors" from Jacob (Genesis 37:3).
Tamar (Matthew 1:3), who is in the lineage of Jesus, was highly likely a Canaanite (gentile or non-Israelite) woman. The Bible seems to indicate Judah liked such females (Genesis 38:2). Tamar, after the death of her two husbands Er and Onan, pretended to be a whore in order to entice him to have sex with her. Their relationship produced twin boys, Judah's fourth and fifth, one of which was Pharez and the other named Zarah (Genesis 38).
The Sons
Judah's first two sons, Er and Onan, were divinely killed for their disobedience (Genesis 46:12). The Bible does not give us an exact reason why Er was killed but it does reveal what Onan did that earned him the death penalty from God.
Er, the firstborn son, died before he and his wife Tamar could produce any children. One of the marriage traditions at the time was that a brother, in this case Onan, was duty bound to marry his brother's childless widow and produce offspring in his brother's name. This practice would later be codified by Moses (Deuteronomy 25:5).
Onan married Tamar but then knowingly refused to impregnant her by "spilling his seed" (ejaculating on the ground). God witnessed this act of selfishness and killed him like his brother Er.
And Judah said to Onan, "Go in to your brother’s wife and marry her, and raise up offspring to your brother." And Onan knew that the offspring would not be his. And it came to pass when he went in to his brother’s wife, that he spilled his seed on the ground, not giving offspring to his brother. And what he did was evil in the eyes of the Lord. Therefore He killed him also (Genesis 38:8 - 10, HBFV).
The Tribe
The tribe of Judah would ultimately exceed all the other tribes of Israel (1Chronicles 5:2) even though the birthright blessing came to Joseph (Ephraim and Manasseh).
The tribe of Judah was chosen to lead the first set of Israelites out of their wilderness camp as they wandered the wilderness for forty years. The tribe was chosen not only because it was the most numerous, but also because it was prophesied that the scepter of rule would never leave them (Genesis 49:10).
Where Did They Live?
Judah lived part of his life in the land of Canaan and then migrated to Egypt when Jacob's entire family moved to the country due to drought (Genesis 46). The next few generations of his genealogy, Hezron, Ram and Amminadab, lived their entire lives in Egypt.
Nahshon, however, lived part of his life in Egypt but was among the Israelites who left the country in the Exodus. He was considered the leader or captain of the tribe of Judah when the Israelites wandered the wilderness for 40 years (Numbers 2:3, 10:14, 1Chronicles 2:10). Although he died in the wilderness like the rest of the disobedient Israelites, his descendants would live in the Promised Land.
A Blessed Genealogy
Rahab (Matthew 1:5) was a non-Israelite harlot living in Jericho. Because she helped Joshua's spies who were in the Promised Land, her life was spared when the city was destroyed (Joshua 2, 6). After she was saved she chooses to live among the Israelites (Joshua 6:25) and marries a man from the tribe of Judah named Salmon (see also Luke 3:32 - 33). They produce a child named Boaz who will also marry a non-Israelite woman named Ruth (Ruth 4, Matthew 1:5).
The descendants of Judah's son Pharez were so esteemed among the tribe that his name was used in the blessing given to Boaz upon his marriage to Ruth.
"And let your house be like the house of Pharez, whom Tamar bore to Judah, of the seed which the Lord shall give you (Boaz) of this young woman (Ruth)." (Ruth 4:12, HBFV).
Boaz and Ruth, through their son Obed, become the great grandparents of King David!
Jesse's Children
Jesse, based on 1Samuel 16:10 and 17:12, had eight sons. That said, 1Chronicles 2:13 - 15 only lists seven (Eliab, Abinadab, Shimea, Nethanel, Raddai, Ozem and David). It is unknown why 1Chronicles lists only seven. Jesse's two daughters were Zeruiah and Abigail (1Chronicles 2:16).
King David
Noah, in the Bible, represented the tenth generation of humans on earth. Abraham represented the twentieth and Boaz the thirtieth. King David represents the 33rd generation.
David is anointed Israel's king, c. 1025 B.C., by the prophet Samuel. David was around fifteen years old when he was anointed. He wouldn't, however, rule over the tribe of Judah until he was thirty and over all the tribes of Israel until he was roughly 37.
David, the eighth and last son of Jesse, is mentioned by name in 28 Biblical books (19 Old Testament, 9 New Testament).
The period from the birth of Judah to the birth of King David, shown in the genealogy chart, is about 672 years.