Borel was the son of the later Major General and Governor of the Royal Military Academy George Frederick William Borel and Suzanna Elisabeth Marcella. His mother was a descendant of the genus Marcella , and a granddaughter of General Bernard Johannes Cornelis Dibbets . He had a younger brother, Eduard Arnold, who died at the age of almost 16 and an older sister, Julie Desirée Borel (1867-1933), married to assistant-resident Eduard Ludwig Martin Kühr , civil servant in the Dutch East Indies . A nephew, the son of Borel's uncle Harry Hubert Borel, was George Borel, lieutenant-to-sea second class, who died in the disaster with the Rammonitor Adder . Another nephew, son of his uncle Henri Ferdinand Borel, was later Lieutenant General Jean Henri Borel .
Borel married three times; the first time on 8 June 1892 with Maria Christina zur Haar, daughter of Franciscus Egbertus zur Haar, music master, and Anna Maria de Jong, the second time on 10 December 1902 with Helena Maria de Hartog, daughter of Henri de Hartog, tobacco merchant, and Carolina Manson, and the third time with Anna Maria Huffstad. From his marriage with Helena Maria de Hartog his son, the later actor Louis Borel , was born. He also had another daughter, Machteld L. Borel, from his third marriage.