When I was about 12, my 9 year old sister came up to me and said "I want to show you something".

I did not know what she wanted, but I followed her to my parent's bedroom. She opened a dresser drawer and pulled some magazines from under some shirts.

"Look at these!" she said and held out some Playboys and Penthouse Magazines. We put them on the bed and looked at them together. I was so hard and more than a little embarrassed and I really wanted her to go away so I could enjoy them in peace. Finally she got bored and went downstairs. I took out my cock and began stroking it to the pictures, and in a few minutes had experienced my first ejaculation. Thanks sis!!