My condolences on your loss, and my sincere sympathy for your having to respond to so many family needs. If your brother is receiving $1549 per month, his benefits are Social Security disability, not Supplemental Security Income (SSI). Social Security is an insurance program and does not require ongoing financial eligibility. Your son's benefits may be Social Security, but more likely SSI, which does require proof of ongoing financial eligibility. If your brother does not live with you, functioning as his representative payee does not affect your son's benefits, because it must be spent entirely for your brother (and annual reports showing that are required). If your brother does live with you and your son, the Social Security income of your brother could be "deemed" to your son, causing him to no longer be low enough in income to qualify. The service representative at your nearest Social Security office are usually pretty well trained and can accurately predict an effect on benefits. You may have to wait in line, but the information will be worth the wait.
Best wishes for a favorable outcome and please remember to designate a best answer.
This answer is offered as a public service for general information only and may not be relied upon as legal advice.
Based on the amount that your brother receives this sounds like he is receiving disablity benefits and not SSI beneifts. Because the money that a person receives as a payee are for the benefit of that person and should be spent on his needs, it should not impact your son's benefits. I would agree with the prior answer that if your brother lives with you and some of your brother's money is used to pay living expenses for all of you, some of that money may be "deemed" to your son.
This information is provided as a public service to provide a general answer and should not be relied upon as legal advice.