en_tn/psa/053/002.md

the children of mankind

This refers to all people.

who seek after him

Seeking God as a person would look for someone is spoken of as "seeking" God. Possible meanings are 1) wanting to know God. Alternate translation: "who want to know him" or 2) worshiping God. Alternate translation: "who worship him" (See: rc://en/ta/man/translate/figs-metaphor)