Solved
All three work but don't make enough money to support themselves.
You say that your sons are "adults" but have not provided any other details. If they are older than 18, and are NOT full-time students, and earned more than $4700 in 2023, you cannot claim them as dependents. And...if you cannot claim them, you do not enter anything about them on a tax return.
Use this IRS tool to help you determine if any of your three sons can be claimed as your dependent.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
https://ttlc.intuit.com/questions/3113432-who-can-i-claim-as-my-dependent
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