My grandfather was Manuel Cuyugan, brother of Carlos, and son of Vicente. Carlos had one child, "Nuning" Cuyugan-Oppen, mother of Gretchen Oppen-Cojuanco. Manuel and his wife Consuelo Granda-Cuyugan had five children (oldest to youngest): Carmen, Vicente, Antonio, Jose and Rosario (b. around 1912). Consuelo was the godmother of the only son of President Quezon.
I could be wrong, but Carlos was not a Santos-Cuyugan.