This happened when I was about 28 (m), and I was dating an 18-yo girl called Katie who was still living at home. Her mom had her very young, so was mid-thirties. Both of them were stunning in different ways. Katie was what I'd call an emo-chick, baggie clothes, long black hair, a fringe and a nose-piercing. Katie's mom (Jess) was more of a typical blonde (dyed) princess type, hot, but she knew it, she'd been divorced for a few years.
It's important to note that Katie and I did have a safe-word, so she could've stopped at any time during this, so her acts in this story were all consensual.
I came over to spend the weekend with Katie as her mom was going to spend the weekend with "friends", Katie was wearing baggie jeans, but with a short top, showing her flat stomach, she definitely wasn't wearing a bra. Not realising her mom was still there, I immediately kissed her and started grabbing her tits.
Katie's mom shouted: "At least wait till I'm gone!". I noticed her standing there in a very revealing short skirt and frilly blouse, very hot. Before she left, she told Katie "be safe, condoms are in the drawer", I laughed, but Katie whinged at the comment. After her mom had left, I told Katie "You know what to do", and she immediately got on her knees and undid my trousers, she started sucking my cock.
After she got me good and hard, she said the magic words: "want to do it in my mom's room?" I laughed and said sure, so we walked to her mom's room. When we arrived, I immediately said "I think I should fuck you in your mom's underwear. "Nooo", Katie replied, as she pulled down her trousers, revealing her shaved pussy, "Just fuck me like this." I found her mom's underwear drawer, and found a bits of very revealing black-lace lingerie, I laughed "wow, your mom's a little slut", then I threw it at her, and told her "wear it."
While she was undressing and put on her mom's lingerie, I opened her nightstand drawer, and found a huge black dildo. I told Katie to come over, she looked so hot in her mom's lingerie, it really accentuated her frame, their bodies were quite similar, but the mom just wore more tightfitting clothes to show it off more. I showed Katie the dildo and told her to "suck it", "no, gross, it's my mom's" she replied, and I said "I wasn't asking" and pushed her on it. "Does it taste like her?" "You're gross" she said as she pushed me away. Then I saw a little SD card. I grabbed it, and told Katie to get her laptop.
I put in the SD card and on it were five video files, we both knew exactly what we'd found, Katie said "I don't want to see that", I asked: "are you using your safeword?" She contemplated for a moment, and then hesitantly shook her head. I started the video. Katie's mom Jess was setting up the camera, and stepped in the frame, she was wearing a darkblue see-through babydoll and did a little twirl.
Then she got on her knees, closer to the camera, and told someone to "get in the shot", a man appeared and Katie gasped as she saw her mom undo his belt, revealing a massive black cock. I paused the video and said "are you okay to continue?" Katie replied: "you're in charge", and I pressed play. Her incredibly hot mom took the man into her mouth, I pushed my hand between Katie's legs, she was so wet. Sadly, the man didn't last more than two minutes, and covered Jess in cum. She posed for the camera a bit, and turned it off.
I moved behind Katie and pressed play on the second video, I pushed her panties aside, as we watched her mom get on all fours. We watched her mom take it doggystyle as I fucked Katie sitting up from behind. She was so horny at this point that it only took a few thrusts to get her close "don't make me cum while watching my mum" she said, as I pushed her into doggystyle too, and fingered her from behind. Her body convulsed as she came while watching the screen. I came inside her and pulled out, I grabbed her mom's big dildo, and pushed her on her back.
I pushed the dildo inside of Katie while the black man on screen got on his back, and we watched Jess ride him. Katie came a second time as we watched her mom orgasm too. I released Katie, as we watched the man finish inside her mom. Katie looked very embarrassed, and I kissed her to soothe her. That weekend, we did end up watching the other videos too, they were a lot more... intense. But that's a story for another day.