This is a subject I've thought about for a long time now. What is God's sex? The answer I've come to is that he is both Father and Mother, and I'll explain my reasoning. Also, to alleviate confusion, from now on I will not use any pronoun in place of "God".
The first thing I'd point you to to find out the nature of God is to the nature of Man. If "...God created mankind in [God's] own image (Genesis 1:27)...", than we are the perfect place to start. Many would stop me there, saying we're not a good example because of sin, but sin hasn't changed what we are, "because even temple ruins point to you an architect even if the temple is shot" (Jefferson Bethke, "The Greatest Artist of All Time"). So just go with it for a minute.
We, each and every one of us, has an intricate balance within us. We all have "Male" and "Female" energies in our souls, spirits, whatever word you use for the essence that makes You. Sure, our physical bodies define our physical sex as male or female, but this has more to do with the mind and heart.
I'm sure most of you are familiar with the concept of left-brain and right-brain thinking, but a brief description is what I'll give here. These concepts are based on the idea that people have two ways of thinking, with their "right-brain" or their "left-brain", and these are the two extremes of thinking. "Left-brain" thinkers are analytical, strategical, practical and logical; they like things in charts and categories and for everything to be organized. "Right-brain" thinkers are expressive and creative and search for feeling and passion; they're care-free, go-with-the-flow and more artistic people. Just Google "left brain right brain test" and you'll find a million tests to determine which you are.
However, most of us are not that black or white. The majority of those tests just determine which you lean more towards, not absolute. Some will say how much more you lean closer to one than the other, as we all have our various levels of how messy we can stand our rooms to be and how creative we can be. We use both sides of our brain all the time. If the left side, logical, practical, analytical, is Male, and the right side, creative and expressive, is Female, then we have both.
I'm not into much science, but I remember from Biology that we all produce both testosterone and estrogen, the hormones that make us either male or female, as well. Males just produce more testosterone and females more estrogen to keep the species alive, but again both Male and Female elements exist. Even in nature we see plants that have both male and female parts, and species of frogs able to switch sexes based on their environment.
So now we get to God, and first a few generalizations. So God is the perfect creator of everything, and man is made in God's image. So God is us, except that God is the absolute perfection. To apply a little logic here, if we are made in God's image, and we have this balance of male and female in us all, then God should have the perfect balance of male and female.
God is creative, and creativity is a female aspect, yet the known universe follows a set of rules we've dubbed the Laws of Physics, and there's the male desire of organization and order. In the Bible we have scenes of God both smiting and punishing peoples and then showing compassion, forgiveness and love. If we apply our Male/Female spectrum here, too, God meets both ends perfectly, aggression and compassion.
So there's my reasoning. If so inclined, let me know what you think; try that contact me box to the side there, email me, tweet me @writingethan, or any other method you could think of.