maybe not. however, the tax laws determine who can claim a dependent. in any one year, there is only one person that qualifies to do that. the laws don't require that person actually do so but that does not give any other person the right to claim them.
generally, that person is the custodial parent who can claim them as a qualifying child. Your brother wouldn't be allowed to legally claim them - they d be deemed a "qualifying relative" because a parent wh can claim as a qualifying child has a higher priority.
