I was just leaving the office when I got the call from my wife's younger sister, Suzi. She'd missed the late bus and asked if I could give her a ride home. She was standing there, wearing a tight, short skirt, waiting at the bus loop when I drove up. She got in the car, slid across the seat, and gave me a big, wet, passionate kiss.
"Thanks for picking me up, honey. I had such a crappy day. I found out Mary Farley with her big boobs is making moves on my boyfriend. I hate that fucking bitch. And he was flirting with her! I got so mad at both of them I flunked a math test and then I missed the goddamn bus. I'm sorry I had to call you."
"That's OK, I don't mind. I always like seeing you."
She moved over in the seat, turned slightly toward me, partly leaning against the door. The way she sat pulled her blouse tight across her chest. From the little nipple points I could see she wasn't wearing a bra. Her left foot was up on the seat, her knee up, giving me a perfect up-skirt look at her panties. She has such sexy legs, all smooth and curvy and soft. "I see you're wearing the panties I gave you for your birthday."
"Yeah. I let Jimmy peak up my skirt in home room and he thought he was going to get a chance to take them off me tonight. He would have to, until I caught him flirting with that bitch! I thought she was my friend." We drove in silence for a minute then she said, "Damn, after a day like this I just need a really good fuck!"
"Well, Suzi, I shouldn't let a wife of mine go without a fuck when she needs one now, should I? We could swing by the house. Jen's going out after work tonight. We'll have the bedroom all to ourselves."
"I'd like that."
Let me explain how my wife's sister is also my wife.
Marriage is a family affair here on Ephaedra. When I married Jen I married her three sisters, too. And she married my two brothers. That's the way it's done here. Jen and I are the primary spouses. The "married wife" and "married husband". We live together like married couples on most other worlds. The brothers and sisters are our sibling-spouses. One of my brothers is married and his wife is also one of my sister-wives (and I'm her brother-husband). Sex is common and accepted as natural, though not required, among sibling spouses. It's always consensual but, really, who wouldn't consent? Most do. The honeymoon after a wedding usually lasts a full month. The primary couple celebrate their marital bliss and establish their marriage together during that time. After the honeymoon is over they are available for dating sibling-spouses. Each sibling-souse pair will celebrate a "honeyday" as sort of a mini-honeymoon where they spend a whole day together. That's usually when have their first sex.
We pulled up to the house and went in. When we get to the bedroom I can feel some tenseness in her as we kiss. I get behind her and rub her shoulders. I caress her on the neck with my lips and feel her tension ease. I reach in front and start unbuttoning her blouse working slowly from the bottom up. I press my pelvis close to her buttocks. She wiggles in approval. As I get to the last button I can feel the soft, smooth flesh of her round but not yet full young tits. I like when she's not wearing a bra. I cup my hands on her breasts and nibble her neck. My growing cock is starting to strain against the confinement of my pants and I can tell she likes it. I roll her nipples between my fingers and thumbs. "I think your boobs are incredibly shapely and sexy, honey. They make my horny." I let go of her tits and start to take off my shirt. She turns around. I help her slip out of her blouse.