Sexy Fun Times/Wank/Hang/Shower/Leading/Swallow
She looks up at you and smiles. "I want to try," she says.
Seconds later, your knob-head is back in her mouth; she takes a deep breath in through her nose and presses down, but her gag reflex makes her pull back, coughing. She tries a second time, and this time it goes further before she has to lift off. You grab a tissue just in time to catch a mouthful of saliva. She wipes her lips with the back of her hand, takes a big breath and dives down again. " If that's what she wants, " you think and this time you put your hand on the back of her head.
She tenses up, guessing what you got in mind and pushes your hand off. You don't want to risk upsetting her so you lean back and let her do whatever she wants. You are pretty sure that your knob is past her tonsils when you feel your balls begin to tighten and you try to warn her, but she ignores you and soon you're pumping spunk into her throat, making her choke and gag.
As soon as your cock comes out of her mouth she brings most of the spunk straight back up all over your cock and balls. She's coughing and spitting, but instead of being upset, she looks triumphant as if she achieved something she'd wanted to do. You pick her up and carry her into the bathroom.
Moments later you're both under the shower and as the warm water washes the mess away, she flips your limp cock and that starts her giggling and then laughing as she bats it from side to side. That sets you off until you both collapse on the floor of the shower in fits of laughter and giggles.
Eventually, your conscience kicks in. You give her a towel to dry herself and sit down on the toilet seat with a towel over your lap. "What we did is wrong; it's not just how young you are, but you're my sister too," you say.
She scowls at you as only a sister can. "It's not as if you made me do anything. I've been wanting to do that ever since I saw Mom doing it," she says. She's standing in the middle of the bathroom floor completely wrapped in a big fluffy towel and she looks as sexy as hell. Your cock inevitably starts to react.
"You saw Mom with a man?"
"No, silly, I saw her with you, and if it's okay for you to fuck Mom, surely it's okay for you to fuck your sister?"
"So, you spied on us?" You stand up and head off to the bedroom to get dressed.
"Not really I got up in the night for a wee and saw you go in her bedroom. You were in such a hurry, you left the door open so when I looked you were on top of her and I could see your bare ass going up and down. "