Not long ago an old friend told me, in response to my recounting of early sexual initiation, his own first awakening 

 When he was eleven he began sneaking into his fifteen year old sisters room while she was out. He would find and smell her dirty knickers. He did not know why the smell made his little hairless immature penis tingle and go stiff. He would work it up and down between his thumb and forefinger while smelling his sisters panties. Then an amazing feeling arrived. He kept on doing this until two years later some sticky fluid jumped out along with the amazing feeling. By that time, having seen another older boy with a well developed penis wanking, he knew what was happening.