You don't include their income on your return. It would only go on their return if they are required to file one. If they only get ssi or SS, SSDI or a SSA-1099 they don't have to file a return and nobody reports it.
Filing requirements for a dependent
https://ttlc.intuit.com/community/children-dependents/help/do-i-need-to-file-my-own-taxes-if-i-m-a-d...
