Soucie was Mary's married name and we didn't know her maiden name.
We decided to start by trying to find her date of death and so we went to the Social Security Death Index where we keyed in Mary Soucie. We received 6 results but none listed the Birth Year as 1907 - one result listed the Birth Year as 1909.
We changed the spelling by replacing the "ie" with "y" and searched for Mary Soucy. We received 23 results and for 3 of those results the Birth Year was 1907. The Last Residences were listed as Nassau, NY, Anne Arundel, MD and Saint Clair, IL. Since we believed that Mary had died in New York or New England we decided to try find more information about the Mary Soucy who died in Levittown, Nassau County, New York. The Death Date was listed as Nov 1985.
We looked for newspapers in Nassau County and found The Levittown Tribune. However, this newspaper's online archives don't begin until 1997. So we looked for another newspaper in Nassau County and we found Newsday whose online archives begin on October 1, 1985 but we did not find an obituary or any other article for Mary Soucie, Mary Soucy or any other Souci or Soucy for 1985.
We next visited the New York GenWeb project Page for Nassau County, New York. We didn't find anything there and since we are not descendants of Mary Soucie we couldn't purchase a Death Certificate from the State of New York (Genealogy Death Certificates must be on file for at least 50 years). A Death Certificate should provide Mary's maiden name and the names of her parents. With that information we should be able to determine whether or not Mary had a brother named Otto.
In many cases you can find the death date of a deceased US citizen in the Social Security Death Index.
The Social Security Death Index (SSDI) provides information about deceased people who had registered with Social Security - many people born before 1900 had registered. See our discussion of the Social Security Death Index.