Family Trip to the Lake

At 23 I really didn't want to go to the lake with the extended family, I wanted to stay home and try to lose my virginity. But as my family paid all my expenses and I relied on them for most things, I had no other choice then to go. The lake is owned by the family, and it was their go to place to unwind. Day two I decided to go into the woods to get myself off, so with my porn mag in hand I headed off to find a place away from everybody. I found a place that looked perfect and started reading the mag to get into the mood. I was getting into a rhythm when suddenly my sister 28 said nice looking cock you've there. It's bigger than my husband's cock. She's the eldest of three only girl and I'm the youngest. She had married to cement a business relationship between family companies. Had two children and according to her, her husband 33 had gone off sex after the birth of their second child. So, getting fuck only once a month sometimes two, I was trying to get my pants back on. She than suggested I leave it out for her to look at more closely, in return she would let me see her naked a real woman instead of a picture. I agreed, she got naked and she started to play with it. So, as she had gotten me aroused again, she said she would get me off. She started stroking my cock then started to suck it I barely had time to warn her I was about to cum. She took it all in her mouth and swallowed it, she was now highly aroused herself and offered to let me fuck her. Of course, I was shocked at first, but it was an offer too good to pass up. She took my virginity, not concerned about getting pregnant as she was already on protection, husband only wanted two children. After a rest we fucked again before heading back to the family cabins together. Next day she asked me to go walking with her and again we fucked. On returning to the city, she said to me in front of everyone, if I needed any help with my studies to just visit her. I needed no help with my studies, but the wink she gave me made answer of course I will. My subject I was having trouble with was sexual education defined as actual sex. My sister was really helpful in giving practical instruction and I'm learning quite a lot. So, my visiting her isn't strange as everyone thinks she is helping me with my studies. In a way she is, I really like her teaching methods. Trips to the lake are now high on my list of things I want to do.