Carlos was born in San Miguel, Bulacan, and one of six children to Melecio de Guzman Santos and Miguela Magpitang Antonio.

There he met Juan's youngest sister, Caridad, his future wife and mother to his children: Rosario, Milagros, Paz, Lourdes and Carlos, Jr.

His first exposure to the INC group was executed under Nakpil's company through the Bishop's Palace in San Juan, Metro Manila.

Each structure was created on functionality that was built with integrity, adorned with 20th-century geometric forms garnished with Gothic revival and Baroque lines.

He also taught architecture at the college where he graduated and helped found the Philippine Institute of Architects in 1938.