You roll her on top of you...

Cathy whimpers as you drive her through a couple of quick orgasms before you stop and hold yourself inside her.

"Hold on tight."

"O-Okay..."

Cathy wraps her arms around you as you roll onto your back, keeping your stiff cock deep inside Cathy's formerly virgin pussy. Cathy groans as she sits upright, feeling the full effect of your long, thick cock in her vaginal channel, her walls massaging your cock before Cathy starts bouncing up and down again, alternating her speed and angles as she does so.

"C-Can I t-tell y-you something, OH FUCK!"

You look up at her and nod.

"D-Don't f-freak o-out, b-but m-my p-parents w-want m-me and m-my s-sister to h-have k-kids a-as s-soon a-as p-possi-"

You cut her off by pulling her down and capturing her lips with yours as you hammer your cock at a rate of knots into Cathy's pussy, occasionally hitting her womb, once she twigs what you are doing, she starts slamming down as you hammer up, before you suddenly pop through into her cervix, making her break the kiss and wail as she cums hard from the deep penetration.

You start breathing harder as your climax draws near, wanting Cathy to cum at the same time, to help pull your life-giving seed deeper into her womb, you start playing with her clit. Cathy cums quickly which triggers your climax, you moan as your cock floods Cathy's womb with a barrage of sperm, helpfully Cathy's orgasm successfully pulled damn near all of your seed into her womb, neither of you move in the aftermath.