Sexy Fun Times/Laid/Park/Frame/Invitation

Just as they are leaving, Susan turns back. "Would you like to come with us," she says with a smile.

The kids seem unfazed by having me along and George just prattles on about some new toy he was given for his birthday. There is a flight of steps up to the door, so you lend a hand with the pushchair. In the hall, George bails out and races his sister to the downstairs toilet, while Susan carries Sophie upstairs, presumably on the same mission. "Why don't you give us a hand," she says. You shrug and follow Alice up the stairs, getting a good look up her dress on the way.

In the bathroom, Alice has one of those kiddy-seats that sit on the normal seat, and by the time you get there her panties are on the floor and she is sat with her dress up round her waist and legs spread wide apart, pissing a steady stream. You look at her and then at Susan, who, busy changing the baby's nappy, seems to be unperturbed by the fact that a strange man is looking at the four-year-old's pussy.

"Come on Alice, I need to go too," she says. She lifts the baby off the changing mat and pushes her towards you. "She needs some cream," she says and tells Alice to fetch it. There's an upright chair beside the washbasin so you sit on that with the half-naked baby your lap.

When Susan drops her panties on the floor, hitches her skirt up, sits on the toilet, spreads her legs and starts pissing, you are shocked. It's one thing with a little girl, but Susan is a grown woman, even if she doesn't have any hair on her pussy. Your cock is uncomfortably hard under Sophie's bottom and you begin to think that this is all too weird.

The door opens, making you start, but it's only George come in to see what's going on, followed closely by his sister carrying a tub of white cream.

You are still not quite sure where all this is going and you just sit there with the half-naked baby on your lap. Alice passes the tub to Susan so she can unscrew the top and then scoop a good finger-full out, which she proceeds to smear on her sister's pussy. "They are like this all the time," Susan says. "I think their parents encourage them - they are some kind of religious nuts who believe that kids should be able to express themselves any way they want. I try to stop them doing this sex stuff but it seems to be getting worse.

George has decided to take his shorts off and is sporting an impressive boner. "Look at him showing off," Susan says. George scoops another finger full of cream and this time he slips it right into Sophie's cunny. Far from objecting, Sophie just giggles.

• Go down for lunch
• Watch the kids fuck
• Fuck Susan
• Fuck Sophie