His paternal grandparents were James Holland Underwood and Ana Pangelinan Martinez, from Tamuning, Guam, and also the maternal grandparents were Juan San Nicolas Taitano and Rosario Sablan Flores, who resided in Dededo, Guam.
His paternal grandparents were James Holland Underwood (dec.) and Ana Pangelinan Martinez (dec.). His maternal grandparents were Juan San Nicolas Taitano (dec.), and Rosario Sablan Flores (dec.), who resided in Dededo, Guam.