This is a generalization that means people from every tribe in Israel came to David, but not every individual. AT: "people from throughout Israel came to David" or "people from every tribe in Israel came to David" (See: [[rc://en/ta/man/translate/figs-hyperbole]])
This idiom means that they are relatives. AT: "we are your relatives" or "we have the same ancestors as you" (See: [[rc://en/ta/man/translate/figs-idiom]])