RobH_en_tn/1ch/15/18.md

With them were their kinsmen of second rank

This likely means that these men served in lower positions and were assistants to Heman, Asaph, and Ethan. AT: "With them were their kinsmen who were in a lower position of power" or "The following relatives would help them" (See: rc://en/ta/man/translate/translate-ordinal)

Mikneiah, Obed Edom, and Jeiel, the gatekeepers

The word "gatekeepers" refers to people who guard gates or entryways. Here it refers to guarding access to the ark of the covenant and applies to Obed Edom and Jeiel. AT: "Mikneiah, and the gatekeepers, Obed Edom and Jeiel" (See: rc://en/ta/man/translate/figs-explicit)