I was thirteen and had just gone through puberty. My older sister Martha (Marty) was fifteen. My hormones were in overdrive at the time but I had yet to discover masturbation. I think every girl should have masturbation explained as soon as they reach puberty.
Marty had been moping around and I overheard her tell our mom that she hadn't gone to the bathroom in five days. That night I was getting ready to go to my room which I share with Marty to do my homework when mom told me to do my work at the dining room table. About ten minutes after I started my pen ran out of ink and I headed for my room to get another pen. The door was halfway open and as I was about to enter I saw mom sitting on the bed with her back to me and Marty lying face down on the bed with her bare butt up in the air under folded pillows.
Yup, mom is giving Marty an enema. Fascinated, I stood watching as neither one could see me. Mom would let a little water into Marty and then stop. At one point she took out the nozzle and put vaseline on her own finger. She put it up Marty's butt and slowly moved it in and out. Mom then took her finger out and put the nozzle back in. At this point I totally knew that I was sexually turned on. It wasn't from seeing Marty getting the enema as much as it was watching mom put her finger up her hole. The second time mom did that Marty began to move her butt slightly up and down. I heard mom say, 'my finger will help move things along more quickly.' She must have kept her finger in Marty for a couple of minutes while she moved it in and out. Little by little the bag emptied. The enema was over and I quickly left and went back to the dining room table. I couldn't focus on my homework because I kept thinking about what I had just seen. That night when I got into bed I began to rub my clit and this time I didn't stop. It really didn't take that long for me to achieve my first orgasm.
A couple of days later I asked Marty if she were feeling OK. I told her I heard her telling mom she hadn't gone to the bathroom in a while. She said she was fine and that mom had given her an enema. I asked her what is was like since I never had one and she said that she really liked it. I thought that was weird since I always thought they must be awful.
My curiosity finally got the best of me and about two months later I pretended I too was constipated and I told mom. Sure enough, she told me what I probably needed was an enema to clean me out. I then discovered why Marty had told me she liked it. The enema was OK but feeling mom's finger in and out of my butt hole really felt good. I discussed this with Marty and she admitted that that was what she liked also.
Since then, about once a month when Marty and I have total privacy we go to my bedroom, remove our clothes and we take turns putting our finger up each others rectums and pumping it in and out. When we finish I always masturbate, I don't know what Marty does.