Micheal Phelp's father

So, I am used to seeing all of the coverage of his mother all over NBC, so I wondered what is the deal with his dad? Don't you think he would come out for at least the Olympics? I figured he was alive since they did not do a somber "swimming for my dead dad" up close and personal piece. So I just dug in the internet, and he may be actually at the games (one website said so, but who knows what it was?). The consensus is that his parents divorced and he is not close to his dad. It is just weird to see his family mentioned over and over without one word about his father.