Segub
The name Segub belongs to two distinct men in the UPDV. One is the youngest son of Hiel the Beth-elite, who dies in his father's project of rebuilding Jericho. The other is a son of Hezron in the line of Judah, born late in his father's life and himself the father of Jair the Gileadite.
Hiel's youngest son at Jericho
In the days of Ahab, Hiel the Beth-elite undertakes to rebuild Jericho, and the cost is paid in his own children. The narrator frames the deaths as the discharge of a prior word: "In his days Hiel the Beth-elite built Jericho: he laid its foundation with the loss of Abiram his firstborn, and set up its gates with the loss of his youngest son Segub, according to the word of Yahweh, which he spoke by Joshua the son of Nun" (1Ki 16:34).
Segub is named at this point in the Kings narrative. He is identified by his place in the family — "his youngest son" — and by the moment of his death, when the gates are set up. The verse pairs him with his elder brother Abiram, whose death attended the laying of the foundation, so that the building of the city is bracketed at both ends by a son of Hiel. The deaths are not presented as accident or judgment on Segub personally; they are presented as the working out of a word spoken long before by Joshua.
Son of Hezron in Judah's line
The other Segub stands in the genealogy of Judah. The line is set out by stages. Judah's sons are listed first, with Perez and Zerah named through Tamar: "And Tamar his daughter-in-law bore him Perez and Zerah. All the sons of Judah were five" (1Ch 2:4). Perez's sons follow: "The sons of Perez: Hezron, and Hamul" (1Ch 2:5). Hezron is Segub's father.
Segub's birth is reported as the issue of a late marriage. Hezron, at sixty, marries into the household of Machir, the father of Gilead: "And afterward Hezron entered the daughter of Machir the father of Gilead, whom he took [as wife] when he was threescore years old; and she bore him Segub" (1Ch 2:21). The marriage joins the Judah line to a Gileadite house, and Segub is the offspring of that union.
The genealogy then carries the line one generation further. Segub becomes the father of a man whose holdings define a region: "And Segub begot Jair, who had three and twenty cities in the land of Gilead" (1Ch 2:22). Segub himself is given no further narrative — the text moves directly through him to Jair and the Gileadite cities.