If use computer software - Family should file income tax together in "one single file", software will optimize for family. System can generate separate return(s) for each individual, hence kid has own return(s).
If use paper forms and done by hand - 如果孩子收入 有扣除$,孩子可 单独报税.
If there were deductions, u can test result with free online software.
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孩子的收入和大人一起报,填在哪一行数字? <= this is when kid has $0 or extremely low income and no deduction. More details in few days.