How to find a long lost family member?

Crazy (abridged) story… my father’s brother was killed in Vietnam and when my sister was researching the war tonight, she came across the virtual Wall Memorial. Upon finding my Uncle’s name, she also came across a comment left by their half brother, Bruce. There isn’t much information but it reveals that he has “sons” and also gives his last name. The comment was left in 2001.

I have cousins! And my father may have a half of a family that he didn’t know existed (he lost touch with Bruce many years ago)!!! I am so excited for him to get in touch with the only (hopefully) living members of his family but I am having a very hard time finding any information. I have typed in his name in Google along with ‘California’ (the last state my father knows he lived in). This revealed an address and phone number, but when my father called, he said the message didn’t sound like Bruce’s voice.

How can I find more about him? I really want to do this for my father, it would mean the world to him. Any help?? Thank you!!!