I was 14 and my sister younger sister was 12, not sure why i did it but one weekend several people stayed over and our grandparents stayed in her room so she stayed in my room on the spare bead, i woke up in the middle of the night to use the bathroom and she was uncovered her night shirt was pulled up and i could see her panties and it turned me on and wanted to see more so i slowly started to pull her tshirt up to see more until her tshirt was abover her hips, she looked so hot so i keept on going and strated to pull her panties off very slowly trying not to wake her up and to my surprise she pretended to stay asleep but casually raised her hips to allow me to o pull her panties off and then she let me spread her legs, and slowly inserted my finger in her pussy and she was letting me do it, then i heard someone opening a door so i covered her and went back to my bead.
The next day she did not say anything and later that day everyone went to eat lunch but i decided to stay at the house so did my sister and as soon as we were alone she came to me and said it is my turn to touch and look and she grabbed my cock trough my shorts i said ok is just fair so i pulled my shorts down and she started to give me a hand job and then started to give me a blow job, i was rock hard and she then said i want to know how it will feel in me do you want to try of course i said yes and she pulled her shorts down and i layed on the floor so she started to slowly sit on me saying it hurted a little until i was deep in her and she said i like how this feels and started to move up and down slowly increasing the pace until she had an orgasm and i came in her soon after we played with each other until i was hard again and we fucked again. Then that night once everyone was asleep she moved to my bead and woke me up to fuck again. After that i would either go to her room or she would come to mine on weekends.
We continued to fuck each other for about 2 years until one time she was late with her period and we thought she got pregnant since i would cum in her, so we stopped after that.