Your sibling's children do not qualify as Dependents for the Eligible Dependent credit.
From CRA web site:
In addition, at the time you met the above conditions, the dependant must also have been either:
Your sibling's children do not qualify as Dependents for the Eligible Dependent credit.
From CRA web site:
In addition, at the time you met the above conditions, the dependant must also have been either:
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