I'm not sure if I can say that I realized that I was gay when I was 13, cause ever since I was I child I somehow lliked men, I always paid attention to guys (especially naked or shirtless) on TV and wished I could touch those guys.
When I was 14 I had a crush on a classmate, but decided not to tell him. Then the next year I fell for another straight classmate, he was a great guy and a good friend, so after telling him that I was in love with someone and talking with him for a couple of months about love (and trying to find out who he fell for) I came out to him. It was … scary, my heart was beating really fast and I was afraid that he was homophobic and would out me to the whole school, but he didn't have a problem with it at all and nothing changed. Later came out to 2 other classmated. After graduation I came out to my cousin, a female classmate and a classmate who had been dating my sis, then my sis. Then one day I found out through my sis that the cousin I trusted most outed me to her mom, who told my mom and her husband, who then told my dad. I planned to come out before leaving home for uni, but then ended up being outed. The good thing is they don't have a problem with that, even though it caused a little "fight" between my parents (they'd divorced many years ago and haven't been talking to each other since then; my dad thought that my mom made up the story about me being gay). During my underclassmen's graduation party, with the help of alcohol, I managed to come out to them and my teachers. After that I came out to a couple of other classmates and others found out about me being gay through those underclassmen.
I feel really lucky to have a family, friends and teachers who are not homophobic and don't have any problems with me being gay, even thought I had a small serious talk with my dad when I was 16 during which he said that he didn't want me to start any relationship cause I might be "confused" and even suggested that I should go to a shrink to make sure that I'm not confused.