Try to warn her

Grandpa's breathing continued to get harder and harder as he bunched up her hair in his hand, holding the side of her head against his thigh. His other hand continued to work his finger deeper and deeper into your girlfriend's ass.

His cock is pointing right at her face! I have to say something.

"Hey ba-"

You warning was cut off by the combined noise of your grandfather loudly groaning, his finger slamming knuckle deep into Carrie's ass, and Carrie whimpering through gritted teeth.

The tip of his engorged cock twitched and a huge wad of cum splattered Carrie's mouth and teeth. "AH! Oh my god what the fu-"

Another rope blasted her lips and cheek. She tried to move her head back, but Grandpa kept a strong grip on her head, laughing and groaning at the same time. "OHHHH YESSS," he yelled, shooting rope after rope over your girlfriend's pretty face. It may have been the biggest load you had ever seen in person. Certainly bigger than any you had ever shot.

When he was done, Carrie laid there stunned, her mouth and face absolutely covered in your grandfather's semen. Still chuckling, he withdrew his finger from her ass and pulled out his phone, snapping a picture before she could object. "My buddy's will love this. Heh heh."

Almost as an afterthought, he took one of her ass and oddly one of her feet, which were up in the air behind her. "Hmm, those too heh heh."

You saw a mixture of shame, embarrassment, and anger come to Carrie's face. "What the fuck, old man? What is wrong with you?!" She demanded.

THWACK! A hard spank came down on her ass and she yelped. "Now look here you little slut. I live here now and if I want to splatter that pretty face of yours, then I will. And you don't say a damn word, boy!" He snapped before you could speak. "Now take that sweet lil' ass into the kitchen and start dinner. I have a friend coming over."

Wiping her face, Carrie turned to you with a look of betrayal, but when she saw the growing stain of precum in your pants, it washed away, replaced by arousal that you were getting off to this. With a wink, she turned back, feigning resignation. "Yes sir. I'll start dinner."

"Now, that's what I like to hear! Son, you've got yourself a real winner there, if she could control that temper. Oh, and honey," he said, grabbing her wrist as she walked away. "These nuts are usually full again in a couple hours." With a wink and a slap on her ass, he got up and walked into his new bedroom.