One day I wont never forget, Mom sat me down in the couch and laid down the news: according to her I was actually adopted. For years she told me that my dad left as soon as she was pregnant leaving her to take care of me by herself. I believed it without second guessing for a second, but apparently she took me in after a friend of hers got pregnant in college and couldn't raise me. "Would you like to know your biological mother?” she asked, as if reading my mind. I gave a quick nod. “If you want I could invite her over so you can get to know her." She came by our house and the first thing I noticed was was her huge breasts.“You must be my son.. Hi, I’m Crystal” She came inside and the three of us sat in the kitchen table in silence for what seemed to be an eternity. "Well, this is awkward." my mom said with a smile. "Let me get us some wine so we can loosen up!" She stood up and left me alone with Crystal. I guess we both realized we were both a bit uncomfortable because we started laughing for no reason.Finally, she said, "this shouldn't be this weird, right?" By the time mom came back with our wine we were already talking like friends. The hours passed and the three of us were having fun and getting tipsier. I was particularly enjoying the stories they shared of their time together at college going to parties, getting into trouble, etc. But, suddenly, they were talking about one time they sort of started an orgy.. They both got really red in the face. Of course this came as a surprise to me. Obviously, I was sure my mom had sex but I could never imagine her in a full blown college orgy. I was ashamed to realize that I started getting hard at the thought. After that story we kept talking for a while before Crystal said she needed to go to the bathroom and my mom offered to show her the way. I was left alone with the image of my mom stroking dicks in her college dorm room, licking pussy, getting cum on her tits. I was so deep in my thoughts I hadn't noticed that 10 minutes had already passed and neither of them were back yet. Curious to see what they were up to I got close to the bathroom and stopped when I heard moaning coming from inside. I peeked inside and lo and behold: Crystal and my mom were topless, aggressively making out with each other.Crystal was grabbing mom's ass and licking her nipples. It was too hot to bear. I took off my pants and started masturbating.They kept at it for a while before Crystal took off moms panties. I could see her beautiful, pink pussy for a second before Crystal started shoving her tongue up and down it. Mom's moans started getting louder and louder, I'm sure I would've heard her in the kitchen. "Try to keep it down," Crystal whispered, "he will hear us...""I don't care!" she responded, "keep going!" She closed her eyes. At this time I noticed Crystal lifted her hand and gestured towards me with her finger to come in. My heart raced. Did she notice I was spying? Was my biological mother inviting me to a threesome with my adoptive mother? Needless to say, I quietly came in and stood next to Crystal ,who was still eating mom's pussy. Still with her eyes closed, mom didn't notice Crystal took my dick with her hand and started stroking. The whole situation was so exciting, I could feel myself starting to cum but I held myself back. Eventually mom opened her eyes and noticed me. "Oh, sweetie..." she said with a sigh. I could tell she wasn't happy about me being there, but Karen's tongue was pleasuring her too much for her to care."Why don't we move this to the bedroom?" Crystal asked as we all started slowly making our way towards mom's room. Crystal laid mom on her back on top of the bed and began making out on top of her. "I want you to fuck me, boy” Crystal requested. I slowly slipped my hard cock in her pussy and started thrusting. "Call me mom," she said, "Call me mom!" We kept going like this for a while. Me fucking Crystals pussy, Crystal caressing my mom passionately and my mom rubbing her clit with her fingers.Mom was being surprisingly quiet, compared to how she was in the bathroom. She was clearly embarrassed with the situation. As time passed, however, I started to hear her moaning again and she even started calling me “My son”. "Your son's dick is so big..."Crystal said softly, "don't you want to try it?"Mom wasn’t sure about it.. But Crystal took the lead.. Crystal gestured me to lay on the bed. As I did, mom got on top of me and started riding my cock. Crystal stood behind her massaging her tits,"Do you like it, son?" Mom asked, "Do you like how mommy rides your big dick?" I did. And I was about to cum.As her moans became louder I could tell she was cumming as well. But then, Crystal said she wanted to ride me too. That she needed her son to cum inside her. So she got on top of me, and starting riding me.She was close to cum, and she wanted me to cum inside her."Do it!" she said, "cum inside me, son."Afterwards the three of us collapsed in the bed..