In July 1999, as narrated by Juan Anastacio Delos Reyes y Santiago (1915-2005), the 21st keeper / archivist of the Familia Sauza-Berenguer de Marquina, he was 16 years old when the 81st Las Familias Unidas was hosted by Don Domingo Cruz y Sauza and wife Doña Inocenta Santos-Cruz on 25 December 1931. During this 81st Las Familias Unidas, Don Anselmo Benedicto Onofre Sauza y Berenguer de Marquina (1838-1940) also known as Abuelo Simong narrated to the clan how Las Familias Unidas came to be.
According to Abuelo Simong, the Familia Sauza-Berenguer de Marquina family tree were written mostly by his elder brother Padre Lorenzo Eduardo Teofilo Sauza y Berenguer de Marquina (1815-1912) also known as Isoy and by his Solis-Sauza and Sauza-Berenguer de Marquina priest relatives namely Padre Soliven Lopez y Solis, Padre Felipe Solis y Marasigan, Padre Luis Solis y Marasigan, Padre Fidel Catigbac y Solis and Padre Claudio Solis y Delos Santos.
His father Don Santiago Sauza y Delos Rios requested the priest, teachers and writer
descendants and relatives to begin collecting information of the family for them to start
writing La Tarcila de la Familia Sauza-Berenguer de
Marquina y Parientes.This was
on 01 January 1850 in Intramuros, Ciudad de Manila, Las Islas Filipinas.
The main purpose of the family tree would be for the first family reunion of the Familia Sauza-Berenguer de Marquina and relatives at Hacienda Sauza-Berenguer de Marquina (1809-1870), the home of Don Santiago Sauza y Delos Rios and wife Doña Ysabel Berenguer de Marquina - Sauza y Sumulong and 11 children. This was located along the riverbanks of Marikina (From the present Tumana, Sto. Niño, Marikina City to Rosario, Pasig City, The Philippines). Presently, part of the Hacienda Sauza-Berenguer de Marquina is the resident block of the Sauza clan in Sto. Niño, Marikina City, Philippines.
Don Santiago Sauza y Delos Rios himself coined the family reunion as Las Familias Unidas or The United Families in English or Ang Nagkakaisang Pamilya in Filipino. On the other hand, the Familia Sauza-Berenguer de Marquina book of ancestry was also entitled "Las Familias Unidas" which was eventually passed to Juan Anastacio Delos Reyes y Santiago on 25 December 1940 during the 90th Las Familias Unidas that was hosted by his parents Don Ysidro Delos Reyes y Manahan and Doña Salvacion Santiago y Robles and family in Obando, Bulacan, The Philippines.