A child's income earned from working is never put on a parent's tax return, the child must file a return in their own name.
Sometimes if the child's only income is interest and dividends, and the child is under age 24, the income can be reported on a parent's return.
If their income is less than $12,950, a tax return is not required unless they had more than $1100 of unearned income (investments, prizes), or their income was from self-employment. If a return is required, you will need to make a separate account. There is a procedure to follow when filing a return for a deceased person.
https://turbotax.intuit.com/tax-tips/family/death-in-the-family/L5albFXM4
