The Mormon believes that he/she existed in spirit form before the earth was created and is co-eternal with God Himself. They also believe they came into existence through a sexual union between their Heavenly Father and Heavenly Mother.
“All men and women are in the similitude of the universal Father and Mother and are literally the sons and daughters of Deity”; as spirits they were the “offspring of celestial parentage.” (Man: His Origin and Destiny, pp. 351, 355.) “These spirit beings, the offspring of exalted parents, were men and women, appearing in all respects as mortal persons do, excepting only that their spirit bodies were made of a more pure and refined substance than the elements from which mortal bodies are made. (Ether 3:16; D. & C. 131:7-8.” Mormon Doctrine by Bruce R. McConkie, 589.
Ask the Mormon why the Jews were always so angry with Jesus and picked up stones to throw at Him. In John 8:58 Jesus told the Pharisees that “Before Abraham was, I AM”. The Jews took this to mean that He equated Himself as God just as when God told Moses in Exodus 3:14; “And God said unto Moses, I AM THAT I AM: and he said, Thus shalt thou say unto the children of Israel, I AM hath sent me unto you.” The Jews were fully aware that no one had existed before the world came into existence, save God alone. The Bible also says this about man in the pre-existence:
1 Corinthians 15:44-47; “It is sown a natural body; it is raised a spiritual body. There is a natural body, and there is a spiritual body. And so it is written, The first man Adam was made a living soul; the last Adam was made a quickening spirit. Howbeit that was not first which is spiritual, but that which is natural; and afterward that which is spiritual. The first man is of the earth, earthy: the second man is the Lord from heaven.”