A breakup can leave you questioning what went wrong. But discovering that your girlfriend secretly slept with your twin brother is the kind of betrayal that can make everything feel surreal.
That is what happened to the original poster. His girlfriend ghosted him shortly before a trip, and while he was away, she went to a party with his twin brother.
After their plans went wrong and they ended up back at OP’s house, they slept together twice. They then stayed in contact until OP came home. His brother eventually confessed, showed him their private messages, and even asked for his blessing to continue the relationship. OP refused, but the entire situation left him feeling betrayed, uncomfortable, and deeply violated.
A man returns from a trip to learn his twin brother secretly slept with his girlfriend
Some betrayals hurt because of what happened; others hurt because of who chose to do it. Discovering that a romantic partner has been intimate with someone else is painful enough, but finding out that the person was a twin sibling can make the experience feel almost surreal. The relationship was not only romantic—it was also embedded in the OP’s family and identity.
The emotional injury here goes beyond jealousy. The girlfriend disappeared before the trip, became involved with the OP’s brother while he was away, and continued communicating with him until the OP returned. The brother then voluntarily disclosed the affair and, remarkably, asked for permission to continue seeing her.
That request may have intensified the sense of violation because it treated an already painful betrayal as though it were a relationship decision requiring the OP’s approval rather than an event that had already crossed a boundary. The OP is also trying to reconcile this behavior with his previous understanding of his brother, making the entire situation even harder to process.
There is another psychological layer worth considering: betrayal can destabilize a person’s understanding of their own memories. The OP may now look backward and wonder whether there were signs he missed, whether the relationship meant what he thought it did, or whether he can trust his brother in the same way again.
Psychologist Dr. Guy Winch explains that betrayal often creates a form of psychological injury because the person who was expected to provide emotional safety becomes part of the threat itself. The resulting distress can involve rumination, anger, confusion, and difficulty making sense of what happened.
That perspective helps explain why the OP describes the experience as feeling “violated.” The word does not necessarily mean there was physical violation.
It can describe the experience of having deeply personal boundaries crossed by people who knew their significance. His brother knew the woman was his girlfriend, and the girlfriend knew she was involved with the OP. The later request for “blessing” did not undo the original betrayal.
The brother’s request for secrecy adds another emotional burden. Asking the OP to protect his reputation after causing the injury effectively places another responsibility on the person who was hurt.
The OP does not have to become responsible for managing how other people perceive his brother. At the same time, he also does not need to immediately tell everyone everything while emotions are raw. Choosing whom to trust with the information should remain his decision.
What matters now is not determining whether the brother’s behavior can somehow be made logical. It may never feel logical. The more useful task is recognizing that the OP has experienced a genuine rupture of trust and is allowed to establish distance while processing it.
Some relationships can eventually be rebuilt after betrayal, but reconciliation is not an obligation. The OP can decide what access his brother has to his life, what information he shares, and whether that relationship can ever feel safe again. Healing does not require pretending the betrayal was smaller than it was.
Sometimes the hardest part of betrayal is realizing that the people who knew exactly where your boundaries were are the ones who stepped across them.
Here’s how people reacted to the post:
These Redditors urged OP to expose the betrayal and stop protecting her brother
These users condemned the brother and ex for an especially brutal betrayal
These commenters shared similar painful experiences of betrayal by their own twins
If someone close to you crossed such a major boundary, would you keep the situation private, create distance, or let the truth speak for itself?
