Go directly to jail, do not pass Go, do not collect $200..
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Your brother can only claim your child as a dependent if one of the two situations below is correct:
Qualifying child rules: Your child is under age 19 or a full time student under age 24, and your child lived in the same home as your brother for more than half the year, and your brother has more taxable income than you.
Qualifying relative rules: Your child's age is not relevant, and your child doesn't have to live with your brother, but your brother must have paid more than half the child's living expenses for the year, AND no other taxpayer -- such as yourself or the child's other parent, can clam the child as a dependent. (If all your income is non-taxable, you are not a taxpayer.)
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Falsely claiming a dependent can result in significant financial penalties. And if the amount of SSI is increased based on you having a dependent, your eligibility can be questioned.
If your child really does qualify, then there's no problem of course.
