Demecio Romo Castilleja, known affectionately as Dei, graced this world on February 17, 1948, in Kyle, Texas. Growing up in San Marcos, he excelled academically, graduating with honors from San Marcos High School before pursuing higher education at Southwest Texas State University. There, he earned both his Bachelor's and Master's Degrees in Chemistry, setting the stage for a remarkable career ahead.

In August of 1975, Dei embarked on another significant journey as he exchanged vows with the love of his life, Yvonne Cruz. Their union was a testament to enduring love and partnership that would withstand the tests of time.

Professionally, Dei's path led him to Dow Chemical Co. in Freeport, Texas, where he served as a Research Chemist. His career afforded him the opportunity to travel the world, forging lifelong friendships along the way. Despite his demanding work, Dei remained deeply committed to his community and church, serving as Grand Knight at St. Michael's Catholic Church in Lake Jackson, TX, among other roles.

Family was paramount to Dei, and he poured his heart into supporting his sons, D.J. and Greg, as they navigated through life's milestones. Beyond his immediate family, Dei played an integral role in organizing the Castilleja Family Reunion for nearly three decades, fostering bonds that transcended generations.

Even in retirement, Dei's dedication to service persisted. He continued to impact lives as a Life Insurance Agent for Catholic Life in San Antonio, embodying the values of faith and compassion that defined his character.

On November 6, 2022, Dei bid farewell to this world, leaving behind a legacy of love, faith, and selflessness. He will forever be cherished by his beloved wife, Yvonne, his sons, extended family, and countless friends whose lives he touched with his kindness and devotion to God.