The idea that "God has a father" and/or the idea that "God was once a man" is not well established in Mormonism. Mormons, like many other Christian denominations (specifically the Orthodox and Eastern Catholic branches of Christianity), do believe in "theosis," the idea that man can progress to become more like God. Historically, this concept (which was had among the earliest Christians) has led some Mormons to speculate that if Man can become like God, perhaps God was once a man. Perhaps He too had a creator, a "Father."
While this idea is interesting, it is not well-established in Mormon theology. I would classify it as "a theological question," not an official "Mormon doctrine." Gordon B. Hinckley, the current president of the LDS Church, has been asked this very question on several occasions. Here are some of his responses (verbatim or reported):
"There was a little couplet coined, 'As man is, God once was. As God is, man may become.' Now that's more of a couplet than anything else. That gets into some pretty deep theology that we don't know very much about...Well, as God is, man may become. We believe in eternal progression. Very strongly. We believe that the glory of God is intelligence and whatever principle of intelligence we attain unto in this life, it will rise with us in the Resurrection."
"President Gordon Hinckley says the concept of God having been a man is not stressed any longer, but he does believe that human beings can become [more like God] in the afterlife."
"On whether his church still holds that God the Father was once a man, he sounded uncertain. ‘I don't know that we teach it. I don't know that we emphasize it...I understand the philosophical background behind it, but I don't know a lot about it, and I don't think others know a lot about it."
That having been said, I'm sure you can find Mormons who do believe God was once a man and that He had a Creator/Father/God. I personally am skeptical. It's not something that is often spoken of in Church; I think I've only heard the concept mentioned a few times in Church during the entire 27 years I've been a member.
To hear two Mormon theologians with differing opinions debate this topic, visit http://mormonmisc.podbean.com/2007/08/27/theology-with-blake-ostler/
If you or anyone else would like to learn more about Mormons from a reliable source, visit http://www.allaboutmormons.com .