Never official doctrine? Check out these quotes:
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Brigham Young: “The man Joseph, the husband of Mary, did not, that we know of, have more than one wife, but Mary the wife of Joseph had another husband. [The babe in] the manger was begotten, not by Joseph, the husband of Mary, but by another Being. Do you inquire by whom? He was begotten by God our heavenly Father” (Journal of Discourses 2:268).
Joseph F. Smith, sixth Mormon prophet (speaking to young children): “You all know that your fathers are indeed your fathers and that your mothers are indeed your mothers. . . . You cannot deny it. Now, we are told in Scripture that Jesus Christ is the only begotten Son of God in the flesh. Well, for the benefit of the older ones, how are children begotten? I answer just as Jesus Christ was begotten of his father” (Family Home Evening, 1972, 125).
Bruce R. McConkie, Mormon apostle and theologian: “Christ is . . . the Only Begotten Son . . . of the Father. . . . Each of the words is to be understood literally. ‘Only’ means only. ‘Begotten’ means begotten; and ‘Son’ means son. Christ was begotten by an immortal Father in the same way that mortal men are begotten by mortal fathers” (Mormon Doctrine, 546-547).
Orson Pratt, early Mormon apostle and theologian: “The fleshly body of Jesus required a Mother as well as a Father. Therefore, the Father and Mother of Jesus, according to the flesh, must have been associated together in the capacity of husband and wife: hence the Virgin Mary must have been, for the time being, the lawful wife of God the Father” (The Seer, 158-159).**
How do you get any more official than these dudes?