The sons of Judah: Er, and Onan, and Shelah; which three were born to him of Shua's daughter the Canaanitess. Er, Judah's firstborn, was wicked in the sight of Yahweh; and he killed him.
The tribe of Simeon had no tribal territory of its own, but dwelt within the territory of Judah (Joshua 19:1,Joshua 19:9). It is therefore dealt with here, immediately after the listings for Judah. Some of the Simeonites’ conquests, which are not mentioned elsewhere, are also recorded (24-43).