Formerly the most eligible bachelor in Singapore, Colin Khoo is dashing, nice, and crazy rich. Like many things in this book, though, appearances can be deceiving. Colin is plagued with "a severe anxiety disorder and crippling depression" (1.17.10). Weighed down by the pressures of taking over his father's business and surviving a wedding that's been turned into a "merger […] choreographed down to the most minute detail," Colin looks the part of the guy who has it all, knows it, and is struggling to find happiness within it.
He and sister Sophie were raised by a single father after their mother passed away. Grandmother Winifred Khoo seemed to help quite a bit, but the siblings were affected by "growing up with only one parent—especially in a place where everyone goes to such great lengths to present a picture-perfect family" (2.13.40). This is a likely source for the mental health issues Colin battles.
Despite all that, Colin is a stand-up guy. He's a grateful friend of Nick's and doesn't waste time telling him so. When it's Nick's turn to wallow in his sadness, Colin cuts his honeymoon short to check on his friend. Colin pushes Nick to crawl out of his funk and "make everything possible" (3.16.54). Colin is exactly the best friend Nick needs.
Fun fact: Colin is related to Nick…kind of! Colin's late mother was sister to Harry Leong—that's right, Astrid's father. So through marriage, these two boys are distant cousins.