As previously stated, probably parents if alive would have priority. You, or they, would have to petition the court. Best advise you can get is to speak with a qualified attorney who practices in (or as close as possible) to Clovis. Sorry for your loss.
You have to speak to an attorney that specializes or practices medical malpractice as there are several key procedural rules you will have to follow before filing your case with the court.
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Did your brother leave a will? If so, it should name the Executor/Executrix of his estate - the person who would usually bring a lawsuit on behalf of your brother's surviving heirs. If he died without a will, most states require the appointment of an Administrator/Administratrix to perform the same role as an Executor/Executrix. Without such an appointment, a suit most likely cannot be filed on behalf of your brother. Also, different states have different rules as to which heirs are entitled to recover for the wrongful death of a relative.
If you seek to pursue a claim, it may be wise to consult with both an estates/wills attorney and a medical malpractice attorney.
In California, there is a specific statute that enumerates who can bring a wrongful death lawsuit. If the decedent's parents are still alive, that would be an important factor to consider. Moreover, if the wrongful death was occasioned by medical malpractice, California requires a Notice of Intent to Sue be submitted to the prospective Defendant(s).