(For clarification both characters are 18 and I believe I made this clear but just in case I am putting this here. Please give me any and all criticism and suggestions for new stories! :D )

Liam laid back on his younger sister's bed as he struggled to attach the tapes around his waist. The smell of overused baby powder mixed with the sweet scent of perfume, accompanied by the loud crinkles and rustles. When Liam had secured himself, he stood up and waddled over to the mirror. He twisted and turned as he admired the look of his brand new underwear. His sister's night time diapers. Liam had always teased his sister about needing to wear diapers for her bedtime accidents but was always too ashamed to admit he was curious as to how they felt. With his parents away and sister out with her friends he gave into his curiosity, posing alone to himself in nothing but a thick pink diaper.

Except he wasn't alone. As Liam stared at him groping the front and back of his diaper he heard a click! He turned to see his younger sister, Anna smiling and giggling with her phone in her hand. "Hehe! Aww, is little Liam getting ready for bed. I have to say they look a hell of a lot better on you than they do me."

Liam's heart stopped as he turned to see his sister, still freshly dressed up from her night out. "An-Anna! I thought you were g-going out for drinks with your friends. T-This isn't what it l-looks like!" Liam stammered with his face turning the same shade of pink as his underwear. He placed his hands over this crotch but it hid nothing at all. He just stood there like a toddler who was caught stealing a cookie from the cookie jar.

"My friends had to cancel so I decided to just head home and now I'm glad I did. You know, I think pink really suits you." She said before taking another set of photos, this time including Liam's mortified face.

Liam held his hands up and yelled. "Anna! Stop!" he started to rush over to her but Anna stuck out her finger and wagged.

"Oh no, no, no. If you try anything I'm sending these pictures start to mam and dad. So you can either behave and do as I say now till they come back, or I can let them deal with you." Anna said with a smirk which bred ill intentions. Liam stopped on the spot like an obedient dog, understanding fully Anna's threat.

"Very clever boy! Now, let get you dressed. Can't be running around the house in just your diapers. Someone might discover your little secret." Anna said in a sarcastic surprised tone. She walked into her wardrobe and returned with a puff pink princess dress and a pair of white thigh high socks.

Liam shuck his head vigorously, "No! I am not wearing that. It's too much." Liam protested.

Anna walked right up to Liam and looked straight up into his eyes, "Oh, I see. Your little sister's diapers she wears for bed wetting is fine but you draw the line at her Halloween costumes. Wear the dress little Liam, or else." She said with Liam's new outfit in one hand and the front of Liam's diaper in the other. Liam felt short of breath as his sister's hand softly squeezed his crotch. Anna's eyes widened a little as she felt Liam's penis start to grow under his padding. "Hehe! Stop pretending you hate this and wear the dress, my little Lily."

Liam's mind went fuzzy whether it was a lack of blood or rush of heat but words were not in his capability. He nodded down to his little sister and put on his new clothes and when he was done Anna circled Liam as she inspected under his dress. "Aww, look at you! You're a perfect lil pampered princess. Now, follow me baby!"

Liam's face was a constant shade of pink. He knew if he did as he told the sooner this would all be over so he nodded and followed Anna downstairs. They went down to the front of the house to the sitting room. Anna patted the couch and told Liam to lay down as she grabbed something from the kitchen. As Liam laid on his back he felt the skirt of his dress riding up. The thickness of the padding stopped him from being able to close his legs so he tried to push his dress down to cover it. Not long after Anna came back out of the kitchen with what looked to be a baby bottle full of milk. Anna handed the bottle to Liam, "Now I want you to drink up all your yummy milkies and I hope it's all done when I get back." Liam nodded silently to Anna as she disappeared back upstairs.

Liam closed his eyes as he suckled on his baby bottle. A burst of sweet tasty milk splashed onto Liam's tongue as he started to drink the formula. He was only half way through the bottle when he heard is stomach growl and churn. Not a second after he noticed this his sister came back with a phone in one hand and a vibrator in the other. Liam's eyes nearly bulged out of his head as he went to spit out his bottle and protest before snapping another photo. "Nuh-uh-uh! I told you to sit and finish your bottle and you're not allowed to move until you do so. So drink up princess."

Liam was both scared as to what was about to happen but more scared about what could happen if his parents saw those photos so he sank back into the couch and suckled like a good baby. "Mmm, that's my good lil boy. Now then!" Anna turned the vibrator on low and started to rub up along the front of Liam's diaper. Liam let out a soft hum as he drank up his milk. His stomach rumbled and ached while his dick grew hard and hot.

Liam was 1/4 away from finishing when Anna turned up the vibrator. Liam gasped as the pleasure grew and his penis start to throb under the muffled vibrations. Soon Liam felt the pain in his stomach intensify. He tried to tell his sister through quivered speech, "A-An-Anna. M-My t-t-tummy hurt."

"It's okay, baby. Just try to relax and I'll make you feel all better." Anna said in a soothing yet malicious tone as she turned up the vibrator even more. Liam found it too hard to focus on drinking the bottle whilst fighting with the cries from his bowels and penis. He opened his mouth wide and moaned, dropping what was left of his bottle onto the floor. He gripped his hands into the couch as he arched his back upwards and pushed further into the vibrator.

Liam could barely control himself as pre cum squirted from his penis and his asshole opened up for what was about to come. His mind wrestled with telling Anna to let him go and keep going as he moaned her name. "Come on, baby. Be a good little girl and let it all out for mommy." Anna encouraged little Liam as he felt himself go over the edge.

In that moment Liam gasped and moaned even louder than before as he reached his climax. His penis throbbed and pulsed before shooting a sticky load of cum straight into his padding and not a second later his bowels emptied themself into the seat of his diaper. The look of pleasure and relief on Liam's face was immeasurable and immortalised by the click of Anna's phone, but Liam was too busy melting in euphoria to care.

Anna placed a hand on the bottom of Liam's diaper and squished, "Wow, looks like someone had to go pretty bad. I think you need these far more than I do. Phew, I better go get you changed. You stay tight baby and I'll be back down in a moment." Anna told Liam who was still panting trying to catch his breath. As he sat there in his padded princess dress with a cum and shit stained diaper he felt glad the worst of it was over.

That was until he heard keys shake as the front door of the house swung open.