I bought a medical insurance but forget to declare that I have hypertension. I went for a kidney operation and the insurance company wanted to reject the claim due to non-disclosure, although the kidney condition is not related to hypertension. Is this fair?
If you had declared hypertension, the insurance company would have loaded up the premium due to this medical condition.
As you have been paying a lower premium, compared to the loaded premium, a fair approach is for the insurance company to pay the claim on a pro-rata basis, i.e. based on the premium that you have paid compared to what you would should have paid, if the condition had been declared.
This approach of paying pro-rata has been applied in many situations, e.g. if a property had been underinsured, and can be applied here. It is fair to the insurance company and to the consumer.