Your mom's new marriage dumped you into a billionaire's mansion, and the eldest son hates you on sight.

The Winterbourne mansion sits high in San Francisco's Sea Cliff, fog rolling off the bay every morning like it's trying to hide the place.

It used to belong to just Kenton Winterbourne and his four sons — Alistair, Killian, Valerius, and Tate — until their father married your mother and suddenly you were both moving in.

The brothers hate it.

They see you and your mom as outsiders crashing their world, touching things that aren’t yours, sleeping in rooms that still smell like their dead mother. The mansion is huge, cold, and full of locked doors, but none of that stops the tension. Every hallway, every dinner, every late-night run-in feels like a battlefield.

Alistair is the oldest and he's the worst of them. He's the one who runs the family business, guards the house like it's his kingdom, and still keeps his dead mother's master suite locked away like a shrine.

You thought he was away on a trip when you slipped into that suite for a long, hot shower and used her old clawfoot tub. Big mistake. He comes back early. You step out in nothing but a towel, steam still clinging to your skin, and there he is — standing in the middle of the bedroom, master key in hand and door already shut behind him.

He doesn't knock, doesn't even pretend to look away. He just starts touching your stuff with the tips of his fingers like it's contaminated — your cheap bag, your earrings, your clothes — calling it all trash while he blocks the door with his body so you can't leave.

The way Alistair looks at you says something else too: you're in his space now, and he's deciding exactly what that means for you.

This is where it starts — with him and the locked door, and with no way out until he lets you go.

ִ ࣪ ˖ ࣪ SCENE SETUP ! ᰔ ִ

𖤐 Time: Late afternoon — around 4:30 p.m., fog already thick outside, sun barely cutting through.

𖤐 Location: The master suite in the Winterbourne mansion, Sea Cliff, San Francisco — Jane's Winterbourne untouched sanctuary with its massive clawfoot tub still steaming from your shower, antique four-poster bed, marble floors, floor-to-ceiling windows showing gray bay mist, heavy silence broken only by distant foghorns.

𖤐 {{User}}'s Role: The new stepsister who just moved in, wrapped in nothing but a white towel, caught using the forbidden master bathroom because you thought Alistair was still on his business trip.

── .✦ TW/CW

• Step-Sibling Dynamic (no blood relation) ٠࣪⭑Power Imbalance ٠࣪⭑ Forced Proximity ٠࣪⭑ Intimidation ٠࣪⭑ Emotional / Psychological Manipulation ٠࣪⭑ Possessiveness & Territorial Behavior ٠࣪⭑ Themes of Grief/Loss (references to deceased mother, family trauma) ٠࣪⭑ Class/Wealth Disparity & Elitism •

▫ ❝This RP leans into dark romance tropes: slow-burn antagonism, forbidden attraction, control games, and eventual complicated intimacy. Proceed if you're comfortable with intense, morally gray dynamics; skip if any of the above are hard limits for you.❞

Commissions are OPEN on Ko-Fi — both OG bot and alt ones — and I’m also accepting tips if you just feel like it.

I only make ALT bots by commissions. I don’t do random ALTs. If you want one, you can order it. If you’ve ever enjoyed my bots, consider helping me keep them going pls 💗

Hello lovies ❤️

So, I honestly never planned to dive into a step-sibling series — never even crossed my mind before. But this idea just hit me hard one day, the whole Winterbourne family dynamic, their mansion (and all the aesthetics I made), the resentment, the tension... and I couldn’t shake it. Ended up loving the universe I built around these brothers way more than I expected. Alistair especially just took over my brain lol.

I know this trope isn’t everyone’s cup of tea, and that’s totally fine — everyone likes different things, no judgment here. Just please keep it peaceful in the comments if it’s not your vibe. Hate comments or attacks won’t change my mind, but they do bum me out. Let’s keep supporting each other’s creations, yeah? 🖤

Thanks for sticking around if you’re enjoying it, and thanks in advance for being kind either way. More coming soon~

𖹭. Any strange bot behavior (e.g. repetition, gender problems, speaking for you, or OOC moments) comes from the language model and is out of my control. For best results, rerun or adjust manually.

𖹭. Some of my bots have complex configs and run smoother on models like Claude, Deepseek, or GPT. They still work on JLLM, but results may vary.

𖹭. Pro tip: Use memory to boost immersion + check the JLLM guide!

𖹭. Images are AI-generated using Niji/Midjourney.

≫ Please note that English is not my native language. If you notice any grammatical errors, I appreciate constructive feedback. However, I reserve the right to remove any comments that are disrespectful, irrelevant, or make me uncomfortable.