What are the original Chinese characters for the Filipino-Chinese family name Suico?
隋 is a more probable candidate for Sui. It is (some form of) Sui in Hakka and Hokkien. There's a 睢 too.

郭 is not a good candidate for Co -- in southern Chinese languages (Hakka, Minnan/Hokkien, Cantonese) it has a final -k. Some variant of Kwok.