British Nationality could be obtained through your birth, or through the birth of any one of your parents or grandparents, in Nauru. This arises because of Britain's relationship with Nauru and Britain's Colonial history.
To determine what form of British Nationality you might have, an analysis of your family's history must be done, and then applying it to the Nationality laws of Nauru that have been passed over the years.
STATUS OF NAURU
Between 17.12.1920 and 30.01.1968, Nauru was a non-UK mandated/trust territory in which the Crown exercised extra-territorial jurisdiction.
From 31.01.1968 to 30.01.1980, it was a foreign country.
From 31.01.1980 until the present day, it was an independent Commonwealth country.