Decided to seduce my Sister

Our family is quite well off, and I get just about anything I want. At 22, going to college, I became bored and needed a challenge. I found my challenge in my sister, who is 2 years younger than me. I believe she is quite attractive, but she doesn't dress to impress, as they say. A bookworm prefers reading to everything else, except horse riding. Will go horse riding anytime she can; the family owns a property where we keep horses. It would be a great way of getting my sister to myself so I could seduce her. My sister doesn't go to the property alone, so her time riding depends on the family: my parents or me and my older brother. But my parents are usually quite busy, and our older brother is recently married and is otherwise unavailable. My goal was to take my sister's virginity and give her some real-life experience. So, I asked her if she wanted to go horse riding on the upcoming weekend, staying overnight Saturday and returning Sunday afternoon. She was very excited to join me; it would just be us, and the caretaker lives in a cottage well away from the family house. I wanted my sister to enjoy the experience, so I planned to take my time. Once at the property, we saddled up and rode around for the rest of the morning. Returning for lunch, we then got other horses and went riding again. During the night, we talked; I made no move on her. The next morning, riding again, then lunch, and then headed home. On our way back, I asked whether she wanted to go again next weekend; she said yes, please. We got closer each weekend we went riding; I was waiting for just the right moment, as they say. Then Fall came the weather got colder, especially at night; my sister started cuddling up to me. But we went to separate beds; my actual chance, not at the property but at home, our parents were away. My sister was studying biology and doing a report on the reproductive systems of life. Pictures of different animals reproducing and their sex parts weren't cutting it. I saw a chance to at least get her naked. So, I said I'll show you mine if you show me yours, not really expecting her to agree. But she and she looked better naked than I had visualized. Nothing other than being naked happened together. But I was now fully determined to bed her; she also trusted me totally. It was two weeks later at the property, after an afternoon of horse riding; she said she was going to shower. Without thinking through, I asked her if she wanted me to wash her back. I thought for a moment I had blown it, but she looked at me, smiled, and answered I'm game if you are. I was game; still, nothing more than washing each other's bodies happened. But I was getting closer to my goal; again, the following weekend, back at the property and showered together again. That time I started fingering her, and she didn't try to stop me. We kissed with tongue, but no sex followed. Oh, so close. I decided to at least lick her out next weekend. But it had to be put off; our grandmother had a heart attack and survived, and we couldn't leave the city until she was at least out of the hospital. Two since last trip to the property we got back there, but it started raining even before we got there, and the wind got colder. I thought it a bust, believing my sister would probably want to return home. But she decided to stay, and she started reading; I sat on the lounge she joined there, snuggling up to me. With her reading, I started feeling her up, and she didn't tell me to stop, so I kept going a little further. Soon I had my hand in her panties, fingering her. She suddenly got up, removed her coat, dress, panties, and bra, and sat down next to me, snuggling up again. A green light, if ever I have seen one, after fondling her breasts and fingering her pussy. I got up, undressed, and got back on the lounge on top of her. She said NO, not without a condom; I'm not protected. I had condoms and decided the bedroom would be better, even though the rain had stopped; we didn't go horse riding that weekend. We are still lovers months later; the only change is my sister uses protection now. Ever willing, I still date; my sister doesn't; she said she prefers our arrangement.