These are their generations - As Shem was reserved until after Japheth and Ham 1 Chronicles 1:5-16, because in him the genealogy was to be continued (Genesis 10:2 note), so Isaac is now reserved until the other lines of descent from Abraham have been completed. The same principle gives the descendants of Esau a prior place to those of Jacob 1 Chronicles 1:35-51; 1 Chronicles 2:1.
Related Commentaries of 1 Chronicles 1:29
1 Chronicles 1:29
29 These are their generations: The firstborn of Ishmael, Nebaioth; then Kedar, and Adbeel, and Mibsam,