I first realized I was an atheist when I was about 12. I never had really thought about it up until then.
I was raised in a house without religion. My father was raised a catholic and my mother a Methodist Episcopalian Lutheran mix thing. Apparently, my dad hated the mad Catholicism impressed on him, and totally denounced God. So I in turn was raised not thinking about the things I suppose normal children do. I was raised without two things: God and Santa. It wasn't as though there was some great void in my life, however, it was just that those things weren't thought about or spoken about in our house. We didn't really pay any mind to them.
When I was about in the 4th grade (at a new school), my friends and I would discuss God and religion and Heaven and Hell. I would try to get myself to believe, and I would try to fit in. I knew I was lying to them, and myself, but I couldn't be the odd one out, because kids can be so cruel. I even started to go to a weekly youth group at a local Methodist church, in junior high, and I would attempt to go with the activities, but I would avoid talking about God directly, and I couldn't pray out loud, as they sometimes did.
I felt so out of place.. There were all of these kids showing how their lives had been affected by God, and the church, and I couldn't add on to conversations about things like that. I had only been to real church about 5 times in my life.
I knew I didn't believe in anything. I had tried Buddhism, and Christianity, and Unitarian Universalist religions, all without any type of major epiphanies. I thought about everything in my life, about everything bad that had happened to me, and how I am such a moral person in such an immoral world... No drugs, no sex, and only a little bit of rock and roll. Some of my friends attempt to be self righteous Christians who go out and have sex and then tell me that I can't say the Lord's name in vain. I realized that my religion (or lack thereof) should not matter, I can still be a good person, not worrying about where I will be when I am dead, or whether I will be at all.
I was raised with the inability to believe in anything without supporting facts to back it up. Religion has not offered me anything that I need. I have no use for it, when I have support from people in my life that I know are there, or at least, they are tangible. I may have no faith in a higher being, but I believe, at the age of 15, I am a very able person. I have the ability to know that I can rely on myself, and I don't need religion to help me... But hey, to everyone that does, good for you. I sometimes wonder what it would have been like to have been brought up in a house with religion and Santa.