They both made over $3900 last year so need to file on their own.
For an undergraduate college student that was under the age of 24 on Dec 31 of the tax y ear, their earnings do not matter. They could earn a million dollars and still qualify as your dependents.
Even if they are required to file their own tax return, that does not prevent them from qualifying as your dependent, and does not prevent you from claiming them as your dependent.
If the student is required to file a tax return and qualifies as your dependent, then the student must select the option for "I can be claimed on someone else's tax return". Note that it does not matter if you actually claim them as your dependent or not. The key word is "QUALIFY". If you the parent qualify to claim the student as a depdendent, and that student is required to file a tax return, then the student must select the option to indicate they can be claimed on someone else's tax return.
