When your husband bought his life insurance he named people as the beneficiaries to the policy.
Each beneficiary is designated a certain amount or percentage of the proceeds form the life insurance policy.
Maybe your husband named his parents and brother as beneficiaries and stated that they should receive 2/3's of the death benefit.
In order to receive money from a life insurance policy the person(s) must be named as a beneficiary to the policy.
Here's how you can learn more about the beneficiary of a life insurance policy and how it works.