The word "them" refers to the other kings who died and were buried properly. Joining them in burial represents being buried as they were. Alternate translation: "you will never be buried as other kings were buried" (See: [[rc://en/ta/man/translate/figs-metaphor]])
This can be stated in active form. Alternate translation: "no one will ever speak again about the descendants of evildoers" (See: [[rc://en/ta/man/translate/figs-activepassive]])