I have previously written about the Mormon belief in a Heavenly Mother or Mother in Heaven who is God's wife, and mother to all his spirit children (including you and I).
I have continued to read and meditate on this matter - and have been convinced that a belief in Heavenly Mother is more than just a 'folk belief' as I had supposed, but is pretty-much canonical in the CJCLDS.
This study of authoritative sources by was what finally convinced me:
David L. Paulsen and Martin Pulido,""A Mother There": A Survey of Historical Teachings about Mother in Heaven", BYU Studies, 50/1 (2011)
The reality of a Heavenly Mother has, naturally, many profound metaphysical - as well as theological and practical - consequences.
It should be noted that the reality of a Heavenly Mother seems to be asserted mostly on the grounds of authoritative revelation; but also on 'logical' grounds that since gender - being either a man or a woman - is a fundamental, pre-mortal, mortal, and eternal reality for humans; and since humans are made in the image of God and are of the same 'kind'; it would make sense if this principle extended to God.
The matter of 'where did God come from?' is often answered by Mormons in terms of an infinite regress: our God was once a mortal man who was spirit child of another God - and so on.
(This is monotheist in the sense that there is but one God for us - relevant to us, in our part of total reality; and these other Gods have absolutely nothing to do with us at all - except as a source of our God).
But another way to answer the question of the origin of God is that He always was.
This is what I believe (or what I choose to believe - since metaphysics are essentially a matter of choice, and stand behind Christian doctrine and not necessarily affecting or affected by it).
So, if God always was; was God the creator, the originator of Mother in Heaven? This would mean that God was the (one and only?) exception to the rule that gender is primary and fundamental - because on this model, God had either no gender or contained both genders.
Or was our Heavenly Mother also eternal - was She always? So that God the Father and Heavenly Mother are coeval and were always divine?
In other words, since the Mormon understanding of divinity is within an also-existing universe with laws and realities within-which God operates; the question is whether eternity contained 'the universe' and one God (without gender) - from whom Mother in Heaven later arose in some way?
Or did eternity contain 'the universe' and two Gods - one male and one female?
I choose to believe the second: that there is no exception to the rule that gender is primary and fundamental to Man - so Heavenly Mother was coeval with God the Father: they existed as divinities from eternity.
Note: What about the rest of us? Did we not too exist from eternity? Yes we did - that seems necessary to explain the reality of free will/ autonomy and also evil. However we were individual essences or potentialities with no 'powers'. But only God the Father and Heavenly Mother were divine. They took these essences and we became their children - divine children. The plan of Happiness/ Plan of Salvation is the very long term hope and intention that at least some of us children will choose-to learn-to become 'adult divinities' (if I may put it that way) like to God the Father and Heavenly Mother. Just as earthly children may mature, grow and learn to become like their earthly parents; always children of their parents but now children who are also - in addition - friends. It is a yearning for loving friends to share their universe which motivated God the Father and Heavenly Mother to embark on the extraordinarily complex, contingent, risky and painful plan of salvation and happiness. Within the constraints of our universe it is, apparently, the only way for us to achieve divinity - although we are free to reject the plan, and to reject progress towards divinity and to stop at any point in the path to full God-hood. Speaking personally, I am at this point too selfishly daunted by the idea of suffering the empathic pain intrinsic to full divine parenthood to want to aspire to the highest possible theosis - and would hope to stop somewhere short of that state. But in the course of eternity no doubt this may change.