I can feel the lips, very moist, pursed and pressed against the tip then pushing down engulfing the head in warmth. As they slip over the rim of my co...ck head they grip it softly and tug backward, stretching my penis while creating a lovely ache, then a caress with the tip of a tongue. This process is being repeated over and over again with the occasional detour further down my shaft and then completely off to the tip but never out of contact, as the push back across the head repeats.I barely. Samantha and I looked at each other and back at her s*ster, both wondering if we were going to get in big trouble.The older girl finally started to calm down a bit. “I’m sorry, that just surprised me so much. It was just kind of cute, you know? My little s*ster and my little cousin playing doctor! Can I see it, too?”It took me a moment to realize what she was asking me.“Mary! Stop being mean!” Samantha whined.“I’m NOT being mean! I’m being serious! I’ve never seen a dick in real life before.. We are waiting for inbound passengers.”“Very well, Ma’am. The next space bus scheduled to arrive from Holstein Planet is due in 74 hours and 12 minutes” With that the robot lost interest and powered down again.Next to the passenger bath rooms stood two big shopping bags and she took them. “I prepared a few things for you.”The she opened the door to the Washrooms and said.”Human Females.”A voice responded.” Human Females acknowledged. Bathroom facilities adjusted to selected species.” The. She had certainly made up for making me wait since then. We had experimented a lot since then and she was usually up for any kinky thing I came up with.“We've talked about it before, babe. Are you ready for a threesome?” She contemplated her answer before responding.“Sure.....only if I also get one for my birthday.”“Are you serious? Who would you want for your birthday?”“I don't know, I just don't think it's fair that only you get to fuck some skank and I don't. Besides, who do you want.