Deductions & credits

If the emancipated rule means that he is not considered to live with either parent, then he can't be a qualifying child dependent.  He can be a qualifying relative dependent of whichever parent pays more than half his living expenses, but only if his taxable income is less than $4300.  If his taxable income is more than that amount, or if neither parent paid more than half his living expenses, then neither parent can claim him as a dependent.