Family Medical History inaccurate? Need advise.

My wife applied for a package that includes both term/whole life insurance this year. All the information my wife provided regarding herself is correct. The problem is that we are not very close with her mother-in-law and she tries to hide many things from us. We tried our best to answer the family history portion correctly, we asked my mother-in-law multiple times if she had cancer as she had surgery near her breasts area and at the time of the application she said she had tumors and that it was not cancer so we listed in the application it was just tumours that were removed.

Now multiple months later we asked her again and shes is now saying she thought tumour meant cancer. She is an immigrant so her English is not that good. We are scared that this will affect our claim in the future since we did not disclose that my wife’s family had a history of breast cancer. What can we do as we were not even aware of this, she is telling us now that it was considered 1st stage of cancer and she is on medication after the surgery when she left out all this information when we asked her many months ago.

Can the insurance company fault us for this? How do we have control over what other people say as we cannot force our mother-in-law to provide her medical information to us. If anyone has any advise please let us know.