His final personal return should use his social security number and only include income and expenses from before his death. Any income and expenses from after his death should be entered on an estate tax return which requires getting an EIN for the estate. It will probably have to be mailed in along with the documentation appointing you (or whoever else it is) as the executor of his estate.
An estate is only required to file a tax return if it earns $600 after your brother's death. That doesn't include insurance payouts or assets that he had before he passed. That is new income created by earning interest or sales of property and whatnot.
Sorry for your loss.
@lzedatTT
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