If you do not have the documents, and in particular the birth certificate of the Italian ancestor who emigrated abroad, it is necessary to carry out genealogical research, which constitutes the phase preliminary and most important for the recognition of Jure Sanguinis citizenship.

For the research of data on the family and, in particular, on the ancestor who emigrated abroad, the first step is that of collecting as much information as possible, both from the ancient documents preserved in his own family and through the stories of his relatives, who could know very important details.

In addition to research within the family, fundamental information can be recovered from genealogical and documentary research:

 both in Italy and abroad, in the databases of surnames, in the embarkation and disembarkation lists from ships, in the registers of military service, census, and personal data registers, in residence certificates, in the State Archives and the Parishes and ecclesiastical bodies.

To this end, it is first of all necessary to go back in the family tree and obtain the birth and marriage certificates of every single ascendant in the State of emigration, starting from the closest one.

At the end of this path back, once you have the certificates concerning the son of the Italian ancestor who emigrated abroad, it will also be possible to know important information on the latter, who represents the beginning, and the root cause, of the chain of transmission of citizenship.