I was 18 years old and living at home and my sister Sandy was 20 years old and coming home from college for about a month. The first weekend she was to be at home our parents were needing to be out of town. They were going to be gone from Friday through Sunday and they thought nothing of leaving the two of us together in the house.
My sister and I were very close and we talked and shared most everything with each other. It was my sister Sandy who showed me my first porn video. Sandy had also let me wear her pretty nylon and lace panties as she knew it was something I liked to do. We communicated frequently when she was away at school and we talked openly with each other about sex. Both of us were interested in each other and the feelings we were having.
We had watched porn together several times and the situation progressed naturally. At first we were fully clothed, then another time we both in just our underwear, me in my jockey shorts and Sandy in her bra and panties. It was during our "underwear only" watching times that Sandy made the first move of touching the tip of my hard penis when I still had my jockey shorts on. I saw her nipples clearly erect in her satin and lace bra and she asked me to touch the front of her bra and gently squeeze her nipples.
This activity led to each of us being fully naked when we watched porn and to us stroking each other; Sandy stroking my hard penis and me cupping and stroking her full breasts. She allowed me to run my finger up and down the front of her always wet pussy, but I was not allowed to penetrate her. Of course we tongue kissed each other while all this was happening.
It was around noon on Friday our parents bid us goodbye and left for the weekend. Sandy and I had the house to ourselves for the next two days. It was only after about 15 minutes being alone that my sister turned to me and said;
"I've really enjoyed what you have been sharing with me. Are you ready to have some fun?"
She was very forward and I was very excited that she was so forward.
"Well, I am if you are." I replied.
"I was hoping you would say that. Why don't you go into my bedroom and take off all your clothes. I'll be in and take off my dress and I can show you what I brought for you." Said Sandy.
I quickly did as she asked me to. And as much as I tried to control it I was not able to keep my penis from growing to an almost full blown erection. My long thin cock stood straight out from my body as Sandy came into the room.
"Ohhhhh, that's a very pretty erection! You've gotten really long! Why don't you sit on the edge of the bed so you're not sticking out so far."
"I'm sorry Sis. I can't help it. I tried to keep it soft but it just happened."
"It's okay baby bro. I see you did as I asked in my letter and shaved off all your pubic hair. You look so smooth between your legs....Except for that hard penis of yours. I'm going to unzip my dress and let's see if we can get you a little softer down there so I can show you what I brought for you."
I watched as Sandy unzipped her dress and stepped out of it wearing only her bra and panties. She had on a white satin and lace bra and full cut Olga brand panties with lots of lace around the leg openings and waistband. There was a blue ribbon woven into the lace and she looked very sweet. I could tell her pubic area was fully shaved; it was very easy to see the outline of her vaginal lips in the front of her panties. Her panties were the same style and brand she used to give me to put on as she watched me get a tent pole with my cock in the front of the pretty nylon and lace panties.
"I know you're a bit turned on, but let's see if you can stop that erection and get really soft for me. You haven't had sex with any girls have you?" Asked Sandy.
"No...Not at all. I'm still a virgin." I answered.
"How about stroking your cock and making it ejaculate? Have you been able to do that?" She asked.
"I have stroked it, but I must not be doing it correctly as I am pretty sure I have never ejaculated." I answered.
"That's good. I'm glad to hear that. At school I have been able to experience intercourse with a boyfriend of mine and it is really fun to do." Said Sandy.
"You have a boyfriend?" I asked with a sorry look on my face.
"I do baby bro, but don't worry about a thing. It will not stop what you and I have together." Smiled Sandy.
I relaxed for the moment, and upon hearing my sister had a boyfriend my erection immediately began to soften.
"See little brother. You're getting soft just like I asked you to do. Now see if you can keep soft when I show you what I brought for you to wear."
With that, Sandy pulled out a beautiful one piece teddy that had loads of lace on it and panties sewn into the bottom of it with huge lace overlays.
"Put this teddy on and see if you can stay soft. I'll bet you can't" Said Sandy.
I did as she asked and no, I could not stay soft wearing the teddy. My erection pushed straight out in front pushing the nylon and lace.
"Oh I love this feeling!" I said as I looked in the mirror at my somewhat feminine body.
"I'm so glad, because I've invited my boyfriend Bill over letting him know I want to have sex with him. I'm going to surprise him with the idea that I want you to watch us fucking." Said Sandy.
"Will he like that?" I asked.
"I don't know. But unless he lets you watch I'm not going to allow him to fuck me." Answered Sandy.
"Oh wow. Do you want me in the room with you two? I asked.
"Only if you are wearing your cute teddy. If you want to watch by staying in the closet and looking through the door that's okay too." Said Sandy.