I would say, they only need one another for the initial creation, or bringing into being, of a particular thing. Like, making a rock, either can do without the other, however making "Rock" would require both. Making a breeze is easy, making "Wind", not so much. I think the only exception would be the mortals themselves. After making them, with the ability to make more of themselves(Procreate) I still think it should take both of them to make something that complex. What do you think?