There are four branches in my Italian ancestry on my grandmother's side (all immigrated from Italy). Two of my great grand uncles, Salvatore and Antonio Albanese, came over first probably between 1900 and 1903. After getting established, they sent for the parentsand their two sisters. I can find passenger manifest listings for the parents and two sisters, but not for either of the two sons.
Is it possible the two sons worked their way across (probably didn’t have the money for passage) and therefore did not appear on any passenger manifests?
Are paying passengers the only names that were listed on the passenger manifests?
Are the ship crews manifests recorded separately and can be searched?