I have two sisters, and they're both bitches. I'm eighteen, and my sisters are one and two years older than me. Somehow they became accustomed to teasing me about jacking off. Marin, the younger of the two, walked in on me jerking it. She barged into my room without knocking, and I was naked on my bed really getting into it. She began laughing and hurried out of the room. I was so embarrassed, and it was pretty obvious by the double laughter that ensued that she had told my other sister, Rena.
From then on, they always smiled wickedly at me, and joked with me whenever it was even remotely appropriate. They kept it under control around our parents, but if the three of us were home alone, I just wanted to lock myself in my room. But then they would just tease me even more about being alone with myself. I always stood up to them, but two against one always wore me down. So when I had enough of letting them tease me, I began playing along with them.
If they started teasing me about jacking off, I would agree with them that I had indeed been jacking off, every single time they joked at me. I would describe in detail my masturbation practices. At first, they were always turned off, and I thought they had finally grown tired of teasing me. Especially when I would talk about how much I ejaculated. They would always wrinkle their noses and leave me alone.
However, one day Rena made a quip about me being selfish or something, and that "apparently that's what self-love does to you". Another of her endless masturbation jokes. I was quick to respond about how loving yourself was better than being with a bitch, or something lame like that. Rena turned her nose up at me and walked away.
Marin, however, kind of laughed.
"Geez, Rena is a bitch, isn't she?"
"What? You're just as bad."
Marin smiled. "I know, but we're just having fun with you."
I felt like poking some fun at her. "Maybe you wish you got it as good from your hand as I do from mine."
Marin laughed. "What makes you think I don't?"
I just stared at her. "Don't even tell me you frig yourself, and then tease me about doing it."
Marin glanced around, in case our parents were nearby. Everyone was going to bed, and our parents were in the next room.
"Let's talk in your room," Marin said, pulling me into my room.
She closed the door, and sat on my bed. It was odd for her to be so warm towards me.
"There's nothing wrong with masturbating," Marin blurted. "We just like to tease you about it because it kind of turns us on."
The thought of my sisters getting off with me in mind was kind of arousing. I had never really thought about my sisters having sexual thoughts or masturbating. It was always one of those things that you knew happened, but you never thought about. Now it was all I could think about.
"Rena frigs herself too?" I asked.
Marin nodded.
"Wait, how do you know for sure?" I asked.
Marin smiled. "Because I've seen her. We watch each other."
I suddenly felt my dick pressing against my pants. I had to sit down on the bed and cover my lap to hide it. Marin enjoyed teasing me like this.
"Really?" I asked, very interested. "Why?"
Marin shrugged. "It gets us going. We're not lesbo or anything, we just get off having someone watch us."
"If you're not a lesbo, then why do you have your sister watch you instead of your brother?"
Marin cocked her head. "Because sisters share everything. Besides, we might be tempted to have sex."
Somehow that almost made me shoot off in my pants. Marin caught a quick glimpse of my erection straining under my pants, and smiled.
"We should just agree that we won't have sex, just watch each other," I said. "Besides, we can't do it without protection anyway."
