This is the Mormon understanding, and reading about Mormon theology was where I first came across it.
I am not trying to persuade other people that I am right; but I shall here consider why I personally believe this, and what it is that I believe.
In the first place it is due to what might be termed intuition; in the sense that when I first encountered this idea, my heart seemed to jump and warm; as if I was discovering something true, good and with great possibilities of more-good.
There was an immediate and positive sense... not so much that this was true, but that I wanted this to be true - this came before my conviction that it was true.
Following this I read more about Mormon theology, and realized that the dyadic, man-woman nature of our Heavenly parents was just part of an entire metaphysical understanding of creation (including procreation - the creation of beings including people) as something dynamic, interactive, developing, evolutionary, open-ended, and expanding.
In other words, that creation itself was creative (and therefore creation was not, as I had previously assumed, a done-thing, a closed accomplishment, a finished totality - once-and-for-always.)
I then began to explore the implications of these ideas for myself; using concepts I got from William Arkle (and his reflections on God's motivations for creation); and Owen Barfield, including Barfield's accounts of the 'polar' philosophy of ST Coleridge.
I was also building on a longer-term fascination with 'animism' - with the (apparently innate and spontaneous) tendency to regard the world (the universe) as consisting primarily of beings - all of whom were alive, purposive, conscious - albeit in different ways, at different scales and timescales etc.
The motivation for creation, and why God should have created this kind of creation, was something I had found difficult to grasp (none of the usual explanations made much sense to me). But when I conceptualized God as the loving dyad of a man and woman, then it seemed obvious why such a combination would have wanted to create - including others who might eventually become like themselves.
Furthermore, it did not seem possible that creation had arisen from any state of oneness of self-sufficiency, since this would make creation arbitrary; nor could creation arise from a tendency towards differentiation, because that would lead to meaningless-purposeless chaos.
There must (I felt) have been some kind of original 'polarity' - in abstract and physics-like terminology, there would need to be at-least two different kinds of 'force', the interaction of which would be creation. Coleridge (also Barfield and Arkle) saw this in terms of a 'masculine'-tendency for expansion and differentiation; and a 'feminine'-tendency for one-ness and integration.
But in terms of my (non-abstract) preferred metaphysics of beings and animistic assumptions; 'masculine' and 'feminine' simplifies to just a primordial man and a primordial woman; this would mean two complementary, unlike-but-of-the-same-kind, beings; the love of whom would lead to a desire for creation.
(In the same kind of way that - in this mortal life - love of man and woman usually leads to a desire for procreation.)
At some point I validated this understanding by means of meditative prayer; by refining and asking a simple question, feeling that this question had 'got-through', and receiving a clear inner response.
In summary; the above account is something-like the sequence by which I desired, concluded, became-convinced-by, the metaphysical assumption of God as Heavenly parents; by some such mixture of feelings, reasoning, and 'feedback'.
All this happened a good while ago (about a decade); since when I have been interpreting things on the basis of this framework, and it seems to 'work', so far.
What the real-life, this world, implications are; include a reinforcement of the idea that the family is (and ought to be) the primary social structure; on earth as it is in Heaven; and a clarification of the nature of creation - starting with the primary creation by Heavenly parents and also including the secondary creation of beings (such as men and women) within primary creation.
This metaphysics has further helped me understand both why and how love is the primary value of Christianity; i.e. because love made possible creation in the first place, and is the proper basis of 'coordinating' the subcreative activities of all the beings of creation.
And it helped me understand how creation can be open-ended and expansile, without degenerating into chaos; because it is love that makes the difference.
Also, it helped me to understand the nature of evil; and how evil is related either to the incapacity for love or its rejection. Without love, the innate creativity of individual beings is going to be selfish and hostile to that of other beings: non-loving attitudes, thinking, and actions by beings, will tend to destroy the harmony of creation.
I don't talk much about this understanding, and I often use the generic term 'God'; because it is difficult to explain briefly and clearly that the dyadic God of our Heavenly parents serves as a single and 'coherently unified' source of creation
But God is two, not one, because only a dyad can create, and creation must-be dyadic.
And the dyadic just-is the one-ness of God the primal creator.
Note added: It may be said, correctly, that the above does not depend on the Bible; but then neither does the metaphysics of orthodox-classical theology depend on scripture. We can find resonances and consistencies within the Bible - but assumptions such as: strict monotheism - creation ex nihilo (from nothing) by a God outside of creation and Time, the Athanasian Creed descriptions of the Trinity, God's omnipotence and omniscience, original sin... These are ideas that would not be derived-from a reading of scripture - the most that can be said is that someone who already ideas can find Biblical references that can be interpreted as consistent-with these assumptions. They are (apparently) products of philosophically sophisticated theologians who brought these ideas to Christianity from earlier and mostly pagan (Greek and Roman) sources. Also, these kinds of metaphysical assumption are theistic - to do with a personal god - but not specifically Christian. The salvific work of Jesus Christ (principally: making possible resurrected life everlasting in Heaven) was done within already-existing creation, and Christianity is not therefore an explanation of creation-as-such.