Sexy Fun Times/Shemale/Work/Nanny

The agency you work for provides you with a uniform; underneath the plain short-sleeved polyester dress, you wear a sensible bra and panties and leave your legs bare. On your feet, you wear short white socks and trainers.

• Laura and Tarquin

You've not been to this house before and after the bus drops you at the end of the street you walk along looking at all the big detached houses, each with a front-drive and many with double garages. The house you're looking for is quite large, double fronted with four, maybe five bedrooms and an imposing front door. You ring the bell and a harassed looking woman practically drags you in. "Thank God you're here," she says, as she puts her coat on; "the children are in the kitchen eating breakfast or, more likely, spreading breakfast around." She stops and looks you up and down. "You're new," she says as if it's your fault. "I suppose I better introduce you."

She takes you through to the kitchen which is all stainless steel and shiny wood. Two children, a girl aged about seven and a boy a year or two older, are sitting at a low table eating cereal; they are both in pyjamas and look as if they just got out of bed. The children look curiously at you and when you say good morning, the chorus "Good morning Miss".

"Laura and Tarquin, the woman says, waving in their general direction. She blows them a kiss; "bye darlings; be good for Nanny. Mummy will be home by teatime." With that, she is gone in a cloud of expensive perfume. You hear the garage door and then the throaty burble of a big engine starting up. As soon as it's out of earshot, the children push their bowls away and sit up. "Can we have some ice cream," Laura asks; "Mummy said we could if we ate all our cereal.

You help yourself from the coffee machine on the counter and sit down. "No she didn't," you say, "but you can have some later if you behave yourselves." The children giggle at being caught out in their fib. "I see you're not dressed yet; did you even have a wash?"

"Mummy doesn't make us get dressed unless we're going out somewhere," Tarquin says.

"You don't have to get dressed, but I think you should both have a bath."

The children look at each other and giggle. "You mean together," Tarquin says.

"Do you usually bath together?"

"We used to," Laura says, "but mummy says were too big to share now."

"It's up to you I guess," you say, "but I used to share with my brother until we were a lot older than you."

The bathroom is big; there's a walk-in shower on one side and a bath big enough to swim in on the other. The toilet is one of those fancy Japanese ones that washes your bum when you finish and there's a fluffy rug covering most of the floor; there's a twin his-and-hers vanity suite and a couple of upholstered chairs. "This isn't your bathroom is it," you say with a grin. The kids look sheepish and shake their heads but tell you that mummy lets them use it sometimes.

Tarquin turns the tap on and sets the temperature; the bath fills quite quickly and you sit down on one of the chairs. "Aren't you going to get undressed then," you say.

"Are you going to watch us," Tarquin says.

"I'm your nanny for the day; I've got to stay and make sure that neither of you drowns."

The children quickly strip off and hang their pyjamas over the spare chair. Laura looks as if she's heading towards being chubby; her nipples are more prominent than you might expect on a nine-year-old and when she turns round, you get a view of her nicely rounded butt. Tarquin is slim to the point of being skinny, but although he tries to hide it, you see that his cock is half-hard and quite impressive for a boy his age.

They both climb into the water and sit looking at each other. "Aren't you going to help each other wash then," you say. With a slightly embarrassed giggle, Laura stands up, picks up a sponge, squirts some liquid soap onto it and hands it to her brother. He sits up with his legs sticking out straight in front of him and she stands astride while he uses the sponge to spread soap over her body. "Make sure you do between her legs and under her bottom," you say.

You're pretty sure that this is nothing unusual for these kids. Laura turns round and bends over so that her brother can wash her butt and he drops the sponge and with a quick grin at you, he uses his soapy hand to soap up his sister's pussy and ass. Then it's his turn and when he stands up, you can see that his cock is fully erect. You have exactly the same problem, but yours is out of sight under your skirt.

Laura is obviously no stranger to the sight of her brother's stiff cock and soon has her soapy hands wrapped around the shaft and under his ball-bag. They've obviously realised that you're fully on board with their games and when Tarquin rinses the soap off his cock and stands in front of his sister, she doesn't hesitate to open her mouth so she can suck it in

You watch the little seven-year-old sucking her big brother's cock for a few moments and then stand up, making them jump apart as if they'd forgotten you were there. "I think this would be more fun in the bedroom," you say. If they notice your cock pushing out the front of your skirt, they don't say anything, but just climb out of the bath, wrap towels around themselves and lead you into what is obviously Tarquin's bedroom. It reasonably tidy, with a lot of books on bookshelves and a computer on a desk; there's some sort of construction set on part of the floor and the bed is obviously just as it was when he rolled out of it.

• You show them what's hiding under your skirt