I needed no further encouragement, and seeing mom's pussy lips hanging open, inviting me into her, I plunged into her deep at the first thrust, just like before.
Again, mom gasped. The doctor let go of her buttocks and moved behind me as I started pumping mom furiously.
As I continued my thrusting, in and out, mom bent herself forward a bit more and started pushing her ass back into me, in time with my forward thrusts, so I was penetrating as deep as possible into her.
"Yea, mom, that's soooo... good," I said out loud.
"Oh, yes, fuck me Jacob," said mom, much to my, and I assumed the doctor delight at her words.
"Yes, that right," said the doctor, "Go on fuck her, fuck your mom, Jacob, and Marge, you fuck your son. Mother and son in perfect unison, a son's prick inside his mother's pussy. What could be more glorious!," the doctor continued, urging us on profusely.
I felt something touch my back and close to my legs and I realised the doctor was rubbing her body against me as best she could with my movements as I fucked, and then I felt her arms across my chest and stomach. It felt great.
Needless to say, with all that had gone on before, all this activity had its desired conclusion, and in double quick time, I finally erupted inside mom with a loud groan, which she reciprocated in turn, as I continued to spurt my cum deep inside her for what seemed like ages. As my cum waves eased, and my cock started to become limp, I hugged her from behind, closing my eyes, still high from orgasm, and felt the doctor holding me from behind, pressing her naked body into me. Fuck this was heaven!