AITA for refusing to attend my sister's wedding because her fiancé stole my business idea?

A 28-year-old woman is torn about attending her younger sister’s upcoming wedding. Years ago, she shared a unique app idea with her sister — only to watch her sister’s fiancé launch an identical business, profit from it, and now use that money to fund much of their wedding.

She confronted them at the time, but they dismissed it as coincidence and refused to acknowledge any wrongdoing. Now the wedding is approaching, her parents are pressuring her to attend “for family,” and she’s been told (indirectly) that her sister expects her to photograph the event for free. Feeling betrayed and used, she’s considering skipping the day entirely. Is she the asshole for refusing to go?

‘AITA for refusing to attend my sister’s wedding because her fiancé stole my business idea?’

The betrayal happened years ago:

I (28F) find myself in a really tough spot and need some honest opinions on what I should do. My sister (25F) is getting married soon, and the entire family...

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Her fiancé (30M) stole a business idea from me a few years back, and I'm seriously considering skipping the wedding because of it.

Backstory: I'd been working on a unique business concept for a few years, and I told my sister about it. I thought we were close.

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Fast forward a bit, and lo and behold, her fiancé launches the same damn business, basically stealing my idea and profiting off it. This scheme is what is funding most...

The confrontation was brushed off:

I confronted them about it, and they played dumb, acting like it was "just a coincidence", and they "had no idea". I was furious, hurt, and betrayed, but for the...

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Now the wedding pressure is mounting:

Now the wedding is approaching, and my parents are pressuring me to attend after I mentioned to them that I want to skip it.

They argue that family comes first, and I should set aside my grievances for the sake of my sister's big day. On the other hand, I feel like attending would...

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So AITA for wanting to skip my sister's wedding over this? Should I put aside my feelings and be there for her, or is it fair for me to take...

Additional painful detail about expectations:

Edit for Info: A few of you really wanted to know what the business idea was. I can't go into detail as it is pretty niche and would be easy...

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I can tell you though that is was an app idea, it is identical to the idea I was working on. Also, some people are defending BIL by saying that...

I had been taking part-time entrepreneurship classes at a local college and was teaching myself how to build an app at the time. I told my sister about it and...

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He stole the idea before I had the chance to go through with it and sold it to his buds, now he co-owns it. I think it's also important to...

and from conversations with my parents it sounds like my sister wants me to photograph her wedding for her, but I have not heard anything about intended payment for photographing...

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So by not going not only would I be causing a bit of drama, I'd also be leaving them without a photographer according to my mom. (I *never* agreed to...

Stealing a business idea — especially one shared in confidence with family — is a profound betrayal of trust. Whether legally actionable or not, the emotional and financial harm is real. The fiancé profited from the OP’s intellectual labor, and the sister either knowingly or negligently facilitated it. Dismissing the accusation as “coincidence” without genuine discussion compounds the hurt.

The wedding creates a painful dilemma: attending could be interpreted as tacit forgiveness or endorsement, while skipping risks being labeled bitter or punishing the sister for her partner’s actions. Etiquette experts (including modern takes from Emily Post) agree that guests are not obligated to attend events that would cause significant emotional pain. Family pressure to “put it aside for family” often prioritizes appearances over justice.

The added assumption that the OP will photograph the wedding for free is another red flag — it shows continued entitlement and lack of respect. Relationship therapist Dr. John Gottman notes that unresolved betrayal erodes trust permanently unless met with accountability, apology, and repair. Here, none has occurred.

The OP is not the asshole for protecting her boundaries and refusing to celebrate a union partly funded by stolen work. Attending would likely deepen resentment rather than heal it. The sister’s wedding is her moment — but the OP’s dignity and self-respect come first.

Check out how the community responded:

The Reddit community overwhelmingly supported the OP — NTA — with most viewing the fiancé’s actions as theft and the sister as complicit.

Most called it unforgivable and backed skipping the wedding:

floridaeng − OP tell your mother if family comes first then why did your sister and her fiance steal your business idea? It seems your sister has a unique idea...

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Deucalion666 − NTA your BIL isn’t the only one that sucks, your sister does as well for sharing your idea with him, then acting dumb when confronted. Don’t go.

kurokomainu − NTA This is based on taking you at your word that the idea was so unique to you and he definitely 100% copied from it… They did betray...

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ZookeepergameNo7151 − NTA I mentioned to them that I want to skip it. Don't mention you want to skip it, just say to anyone who asks I'm not going and...

Many highlighted the added disrespect of expecting free photography:

Haggis_Hunter81289 − NTA, forget that BIL stole a business idea, if they assume you will be their photographer without asking, or even offering payment, then I'd not go either.

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Several questioned whether the idea was truly original but still sided with the OP’s right to boundaries:

[Reddit User] − This one is impossible to judge without hearing the idea because everything hinges on how original it was.

EnglishRose71 − Do you have notes, written ideas, that you can prove are back from when they stole your idea? … If you casually mentioned it to your sister, and...

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Refusing to attend the wedding is not about punishing the sister — it’s about protecting personal integrity after a serious betrayal. The fiancé stole a business idea shared in trust, profited from it, and now uses that money to fund the very event the OP is expected to celebrate. The sister’s complicity (sharing the idea) and lack of accountability make forgiveness feel impossible.

Expecting the OP to photograph the wedding for free adds insult to injury — another sign of entitlement. Attending would likely deepen resentment rather than heal it. The OP is not obligated to smile through pain for family optics. Skipping is a valid boundary. Compassion for the sister does not require self-sacrifice. The right to say no exists — even on someone else’s big day.

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