As I'm close to 3 years into managing my father's estate I want to offer some thoughts. IRAs, 401k's, and some other such accounts (inc life insurance) where no living beneficiary was identified still fall outside of probate. This may depend on which state you're in but so far in the two states I'm probated in, retirement accounts are transferred directly to the heirs. The distinction is that, not being part of the estate, they are protected from creditors.
Thus, if the only money your brother has was in retirement accounts and debt claims were filed against the estate, those funds would not be claimable by the debtors. Each company that manages retirement accounts does things their own way, but they all seem to have a process for heirs to claim these funds.
Also, not being part of the probate estate, they can be distributed immediately. Good luck, sorry for your loss. Going forward, everyone should get at least some of their affairs in order. set beneficiaries, make accounts TOD (transfer on death), even if you don't have the gumption to write a Will.
