A/N: I've been playing around with this head-canon for a while now and the addition of Penelope Shepard's character makes this slightly AU. However, I tried to stay as true to the characters and settings as possible.
If I had to put a timeline on it, I would set it somewhere around the middle of season 5. However, Judgement Day and Jenny's illness will forever be disregarded, and I added in the technology of our current time.
Penny is around 8-10 years younger than Jenny and also a member of Gibbs' team.
The entrance hall was dark and quiet when Jenny Shepard entered her house at 3 a.m. that morning. Silently, she slipped through the door and kicked off her heels immediately to prevent the unavoidable noise they would make on the marble tiles. She closed the door and leaned against it heavily, listening for any sounds that might come from upstairs. She could only hear her own breathing and sighed in relief, glad that her sister was evidently fast asleep.
The streetlights illuminated the hall enough for her to navigate her way to the stairs without having to turn on the light and while she walked up, she was careful to avoid the one step the she knew always cracked just loud enough to wake someone up from a light sleep. That was just the last thing she needed right now, having to explain to Penny where she was coming from this late in the middle of a work week.
It was, in fact, also the last thing she herself would have expected to happen when she had left the house earlier and Jenny was not entirely sure of how she felt about the turn of events her night had taken. Pushing all thoughts of possible consequences from her tired mind, she opened the door to her bedroom, making sure with a quick glance over her shoulder that the door across from her was tightly shut.
Yawning, she reached for the light switch and turned towards her bed, only to immediately startle back against the door in shock. Her hand flew to her hip out of reflex, only to find nothing there, when her eyes met with two equally green ones staring back at her.
"Jesus Christ!" Jenny yelled, as a mischievous grin spread across her sister's face. Penny was casually slouching against the headboard of the bed, pillows popped up against her back, her legs crossed underneath her. She was eating chips from a small bag on her lap and looked very pleased with herself.
"Did you really think you could sneak your nightly adventures past me?" she drawled, munching on a handful of chips.
Recovering from the initial shock of being ambushed like this, Jenny drew a hand through her messy red hair, trying to comb out some of the tangles. She had to give up eventually and resorted to pulling it up into a bun, silently glaring at Penny while she put the elastic around her thick hair.
The other redhead eyed her curiously, her head tiled slightly to the side and her grin only grew wider, the longer she stared at Jenny. The latter just remained silent and braced her hands on her hips in annoyance, hoping she could just intimidate Penny into leaving her room again. She soon had to realize, though, that that would remain to be wishful thinking.
Unimpressed, Penny untangled her legs and shifted forward onto her knees, brushing her greasy hands off on her thighs before licking her fingers.
"You fucked him, didn't you?", she smirked and raised one of her eyebrows suggestively.
"For god's sake, Penny! Will you stop eating in my bed? You're crumbling all over the sheets!" Jenny yelled at her, gesturing with her hands and snatched the chips bag off her bed. She crumbled it up and threw it into the trash next to her dresser, ignoring Penny's cry of protest.
"Hey! I wasn't finished with that!"
"It's three in the morning!" Jenny decided to change strategies and resorted to just ignore her sister's infuriatingly annoying presence. She shrugged off her light summer jacket and slipped out of the casual jeans and blouse that she had changed into after coming home from the office. She noticed her clothes already smelled of that distinctive combination of sawdust and bourbon and she couldn't help but smirk a little when she inhaled the scent. She folded her clothes neatly into a pile, put them on top of her drawers and turned around, searching for her nightgown.
"Come on," Penny whined and grabbed the silky pajamas from beneath the comforter, throwing them at Jenny, "gimme all the dirty details. You know I have no sex life and therefore need to vigorously live through you."
She suddenly lunged forward and grabbed Jenny's leg just above her knee making her almost loose her footing.
"Is that a bite mark?" she asked curiously and tried to push the hem of the nightdress up her thighs. Jenny swatted her hand away and kicked her in the shoulder with her knee, causing her to fall over on the bed.
"Can you get out from between my legs, please? Do you have any respect for personal space?" She smoothed out the nightdress over her thighs and noticed that there was indeed a faintly purple mark on her skin. Damn him.
"I bet that's not what you told Jeth-ro in his basement earlier?" Penny drew out the last syllable of his name and bit down on the nail of her index finger, grinning again and very obviously not leaving the subject alone.
"Why?" Jenny asked, more to herself, "why, do I deserve the misfortune of being related to you?" She pressed two fingers to the sides of her head and groaned, slumping down on the edge of the bed.
"Move," she said, nudging her sister to the side and crawling under the covers. Penny rolled onto her side and joined her, popping her arm up on her elbow and resting her head in her hand.
"For the love of god," Jenny moaned, closing her eyes in defeat for a second before focusing them on the ceiling.
"I did go over to his place to deliver the files the FBI had sent in," she began and was immediately interrupted, "because that couldn't have waited until tomorrow, of course". Jenny snapped her head over to her sister and glared, "Do you want to hear this, or not? Because you're really pushing it tonight."
Penny laughed and held up her hands apologetically, "I'm sorry. Go on." She cleared her throat, "You went over to his place without any extremely obvious intentions. Then what happened? You accidently slipped and fell on his - "
"Okay, that's it!" She turned over and started to kick Penny out of the bed.
To her annoyance, her younger sister was still laughing hysterically at her own joke, even when she fell to the floor and landed on her back.
"OUT!" Jenny yelled and pointed to the door, sitting up again.
Penny remained completely unfazed by her tone and glaring and just rubbed the back of her head, giggling. She sat up on her knees again and crossed her arms in front of her chest, trying her best to compose herself.
"Really, Jen?" she asked, "You're really trying to tell me that you have not been looking for an excuse to be alone in his shady basement, a little drunk on that horrific beverage he calls Bourbon and getting it on with him?" She raised an eyebrow, daring her to pretend the opposite.
"Do I have to forcibly remove you from my bedroom, Penelope?" was the only response.
"I'd love to see you try" Penny challenged.
"I have a gun in my bedside-table and I will not hesitate to use it"
"Had." she smirked, and Jenny was about to double check but then decided to just give in to this nonsense. Her hand went to her neck, rubbing it awkwardly and she sighed, "Fine. Regardless of the circumstances that had me going to his place, I did, in fact, have a drink with him. One thing led to another – No, I don't know who made the first move and it also doesn't really matter – And I somehow ended up naked on his counter."
Penny squealed in delight and threw her hands up.
"You're unbelievable. Are you satisfied? Can I finally go to sleep, now?" Jenny shook her head, blushing just the tiniest bit.
"Me?" another laugh escaped her as she jumped to her feet, shaking out a foot that had apparently fallen asleep. "You're the one that just got fucked on a very dusty and unsanitary workbench by her subordinate."
"Yes, I am very satisfied. And if you finally shut up and leave me alone, I might even tell you exactly what he did with his tongue tomorrow morning" she answered and watched with relief as Penny make her way to the door at last.
"See, that wasn't too hard now, was it?" she drawled, turning off the light switch and opening the door, "unlike –"
"LEAVE!" A flying pillow cut off the last part of her sentence and Jenny could still hear her sister's mischievous giggling until she finally reached her own room. She couldn't help a satisfied smile lifting up the corners of her mouth, though, as she finally had the chance to peacefully think about all the things that happened on that unsanitary work bench again.