I think we need to understand that the answer will be different for different people. In all likelihood there is a standard bell curve distribution for the age at which a person realizes their sexual preferences. What you really want to know is the youngest age at which someone might already know their preference. Already the answers from several people on this thread show a scattering of ages. I think I must be a bit of an early bloomer because i remember having impure thoughts about Annette Funicello when I was watching the Mickey Mouse show around age 5. I also remember tripping and falling on purpose the following year in kindergarten when the girls would chase the boys and try to kiss them. Of course I pretended to hate it and fight them off when I got caught and just assumed the other guys were pretending as well but who knows. At any rate, the lower limit is at least 5 yrs old but possibly lower unless I'm the extreme end of the spectrum.How impure can a five year old's thoughts be?