I didnt add my other child I thought his father was claiming him and he didnt can I still add a dependent

[Ashby]

You can add a dependent by going back into the personal info portion of your tax return. Or, you can just search "dependents" in the search box.

If you have already filed, you will need to amend your return to add the dependent.

Here's the link to appropriate amending instructions:

https://ttlc.intuit.com/replies/3288565