Legal Question in Wills and Trusts in California

If your brother is the primary beneficiary of the insurance policy then it now his - it pays out to him and he doesn't have to share it with you. Since you are not entitled to any distributions from the life insurance policy, the life insurance company cannot and will not provide you with any information unless you sue you brother under some sort of constructive trust claim (that is, the claim that your parent named your brother as beneficiary with the intention that he divide the money with the family, or that your brother got your mother to change the beneficiary to him as a result of undue influence or your mother's lack of capacity) and then subpoena the records of the insurance company as part of the trial discovery process.

What you probably ought to do is to consult with an attorney. The big issue here is why your mother named your brother as primary beneficiary instead of naming both of you.