Arianism is the name of that doctrine. Was common in ancient Egypt and northern Europe, is also present in several other Restorationist sects (Jehovah's Witnesses are one).
I don't know that the Mormon authorities ever really clarified this, but I think the general interpretation is that there's a sort of branching and cyclical nature to creation. The Mormon concept of the soul is that it is gendered and they, essentially, reproduce sexually, not necessarily in the sense of being tied to a physical sex act, but that by definition is what two things combining to make copies of themselves is. It's implied that the cycle of reproduction is attached to a cycle of world creation, a world per god. It makes a very interesting contrast to the the static and cyclical views of other religions.