Answer:

Don Cayetano was born in Udyong (now Orion), Bataan to Servando Arellano, a working Spaniard and Crispora Lonzón, a meeting in Bataan. He started as a working student in Colegio de San Juan de Letran. After finishing his high school he transferred to University of Santo Tomas, where he finished his Bachelor of Philosophy in 1862 and Bachelor of Theology in 1867, he then continued studying and finished law in 1876. During the Spanish regime, he was appointed as a Magistrado Suplente of the Audiencia Tribunal de Manila. He later become the Chief Justice of the Provisional Supreme Court created by the military in 1899.

Arellano, together with Pedro Paterno, Benito Legarda, Florentino Torres and Felipe Buencamino, testified before the Schurman Commission that the Philippines was not yet ready for self-rule. Together they formed the Federal Party to "promote the annexation of the Philippines as a state". In lieu of this objective, they petitioned the U.S. Congress to create representation, as well as a Philippine Congress and a federal Court.

Upon the onset of the American civil government in 1901, US President William McKinley appointed Arellano as the first Supreme Court Chief Justice.