A family kidnapped by aliens!

What was supposed to be a normal family gathering turned out to be anything but. In a flash, all of us had been teleported - aunt Petra, my sister Ashley, our mom Rebecca, and me, her son - to a strange enclosure of some kind, all of us missing our clothes. Looking at our surroundings, it appeared to be like a tiny beach, complete with gray sand and a miniature ocean, ending where a large metallic wall began. Said wall encircled the entire area, while up above we could see a reflective surface, like a large, bowl-shaped mirror. Looking around, I could tell we were all in various degrees of distress - aunt Petra and mom seemed completely in shock, looking around with wide open mouth while trying to cover up their nude bodies. Ashley seemed to react the least, but still covered herself reflexively as well. Before we could even react or speak, a booming, nasal voice came across an unseen loudspeaker. "Welcome humans, to a preliminary study on the sexual behaviour of sentient species! We assure you that your lives are not at risk, and that you will be returned to your prefered domicile upon the conclusion of the study!" Everyone shared a look of shock between themselves. "Oh god, aliens?" Mom whispered. "Oh god, what's going to happen to us?" Petra muttered, torn between covering her face in horror and keeping herself from being exposed to stellar visitors. The loadspeaker crackled once more. "Yes, once the purpose of the study is concluded you will be graciously returned to where you were found via our advanced teleportation array. We can assure you that the process is safe, even to lesser minds such as yourselves!" I looked up towards the curved surface above. Was it a two-way mirror? They must be spying on us, seeing everything that's going on. "So, without further delay, allow us to present the purpose of this study!"

All of a sudden the surface above began displaying information - strange diagrams in a language none of us could understand, with pictograms and images of animals and people from Earth accompanying them. Notably, one seemed familiar - that of a stylized man, with a stylized woman. "The purpose of this preliminary study is to gather data regarding the behaviour that less advanced species portray during sexual courting and mating, in particular sexually dimorphic species. As such, we will need the three female members of your species to engage in [colloquialism not translated] with the male one. Preferably several times, for data collection purposes. You will of course be provided with the required nutrients during these coming days to remain healthy and alive! For now, you may proceed."

With that, the loudspeaker went silent. The four of us looked at one another, until Ashley finally spoke up.

"What the fuck!?"