British Nationality could be obtained through your birth, or through the birth of any one of your parents or grandparents, in Samoa. This arises because of 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 Samoa that were passed over the years.
STATUS OF SAMOA
From 17.12.1920 until 12.12.1945, Western Samoa (as it was then known) was a New Zealand Mandated Territory in which the Crown exercised extra-territorial jurisdiction.
From 13.12.1946 until 31.12.1961, it was a New Zealand Trust Territory in which the Crown exercised extra-territorial jurisdiction.
Between 01.01.1962 and 30.01.1980, it was a foreign country. From 31.01.1980 until the present day, it is an independent Commonwealth country