I think the mistake some posters are making here is to argue for blanket rules — either “it’s always fine” or “it’s always dodgy.” Real life is more complicated than that.
For most families, yes, sharing a room might be logistically convenient and totally harmless. But in other families, where boundaries are weaker or where there are existing dynamics of enmeshment or control, it can become unhealthy. That doesn’t mean it’s automatically “incest”, but it also doesn’t mean it’s automatically fine.
One key question is who initiated it. Was it the parent’s idea? The child’s? Did one feel unable to say no? If an adult child and parent are repeatedly making exactly the same choice to share a room or bed, with no discussion and no sense of boundary, that does raise questions. It’s not about being “dirty-minded” , it’s about recognising when a relationship is functioning more like a spousal stand-in than a healthy parent-child bond.
I also think there’s some privilege showing in the idea that this can never be a problem. For people from safe, boundaried families, it’s easy to assume that. But for those from enmeshed or coercive backgrounds, these situations are loaded, and shaming people who voice discomfort only protects the unhealthy dynamics.
It isn’t about criminalising everything or assuming the worst. It’s about recognising the wide grey zone between “healthy” and “incest”, because that grey zone is exactly where many people’s pain and confusion lies.
OP, I'm glad you got out of this relationship for two reasons 1. these things don't get better 2. you risk (as this thread has highlighted) being labelled as the crazy, dirty-minded, jealous girlfriend getting in the way of 'pure love', rather than being honoured as the insightful woman you clearly are. Best of luck.