This should help:
For 2016, Dependents who are not 65 or older or blind, who have earned income more than $6,300, must file their own return. Income levels required to file a return for those 65 and over or blind are higher. You do not include their earned income on your taxes. If they earned less than $6,300 in 2016, they do not have to file a return, but may wish to do so to recover any withheld income taxes. You can still claim the dependent exemption, and the dependent will not be able to claim her personal exemption on her own return.
Dependents who have unearned income, such as interest, dividends or capital gains, will generally have to file their own tax return if that income is more than $1,050 for 2016 (income levels are higher for dependents 65 or older or blind).
A parent can elect to claim the child's unearned income on the parent's return if certain criteria are met. If the dependent child's 2016 unearned income is less than $10,500, he made no estimated tax payments during the year, and he had no income tax withheld at the source, parents can generally elect to claim his investment income on their own return.
https://turbotax.intuit.com/tax-tools/tax-tips/IRS-Tax-Return/Should-I-Include-a-Dependent-s-Income-...
