What happens when insurance proposal form conceals material facts?

Non-disclosure of other policies cannot be a ground for repudiation of an insured person's claim

It is generally found that insurance agents fill up the proposal form on behalf of policyholders. But what happens when the proposal form conceals material facts?
 
Ramjibhai Parmar was approached by Anishbhai Dhirajbhai Vyas, an insurance agent, who persuaded him to take an insurance policy. Parmar took Aviva’s LifeLong Unit-Linked Insurance Policy of Rs 15 lakh. The proposal form was filled up in English by the agent and Parmar merely signed it in Gujarati.
 
A fortnight later, Parmar developed breathing problem and fever. He was diagnosed to be suffering from pneumonia and expired a day later. His widow