Here "Rahab" is a poetic way of referring to Egypt. Both "Rahab" and "Babylon" represent the people. Alternate translation: "the people of Egypt and Babylon" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/translate-names]])
"This one" refers to the people from the nations that the writer mentions. Although they were not physically born in Zion, those who follow God are natives of Jerusalem spiritually. (See: [[rc://en/ta/man/translate/figs-metaphor]])