This happened nearly fifteen years ago but I remember it vividly and still masturbate thinking about it.
It was during the school holidays and my sister Laura and I were alone at home for most of the time as our parents both worked. I was fourteen and my sister Laura was sixteen, despite the two year age gap we always got on well together.
One morning I was standing in my bedroom naked except for my shorts. I was looking out the window watching my sister lying in the back garden soaking up the rays. She was wearing a miniscule bikini that hardly hid anything and I felt myself getting hard. I touched myself through my shorts still watching her and imagining her naked. I knew I should not be thinking about her like that but at fourteen my hormones were on overdrive and this was the nearest I had seen to a naked woman except in magazines. My erection began to throb and I dropped my shorts and grabbed my hard cock and started stroking. It did not take long for me to cum and soon I was gasping as ropes of cum spurted from my hard cock.
At lunchtime Laura shouted that she had made us a sandwich so I went down to the kitchen and grabbed a couple of cold cokes and went out to the garden. As we ate our sandwiches I could hardly keep my eyes from her small breasts barely covered by her bikini top. I could feel myself getting hard and changed position so that Laura would not see. Then suddenly she asked 'Did you have a good view this morning'
I started to go red and mumbled something but Laura said 'I saw you looking at me, were you wanking?'
I started to say something but Laura shook her head 'I know what boys do' she said.
I just got more embarrassed and as I was never a good liar I said 'Yes
'Was this what you were thinking about and she reached round and untied her bikini top. I could not believe it I was looking at my first naked breasts. My cock was throbbing hard as I looked at her. Her body was red from the sun apart from the small mounds of her breasts.
Privacy was not a problem as our garden was fully enclosed. Now she took my hand and led it to her breast 'Touch it if you want' I was shaking as my fingers touched her breasts and Laura said 'Do you have a hard on?'
I nodded and she said 'Well let me see it'
I shuffled around and unzipped my shorts letting my hard cock out. Laura looked at it and said 'Wow' my little brother is not so little' and she put her hand around it. I nearly came there and them as the first hand except my own of course wrapped around my cock. As she moved her hand up and down she asked 'Is this what you were doing earlier'
I could hardly speak and just nodded as she masturbated me harder until I started to pant. I looked at her small bare breasts and immediately started to cum. It was easily the best orgasm I had ever had as streams of cum shot from me landing on her bare thighs and then flowing over her hand.
'You have a lot of cum' she said still holding my cock. Then she let go and stood up, 'I better go and clean up' while I still sat there my cum covered cock shrinking.
That afternoon led to us having more fun over the summer holidays but that is a different story.