After you file

OK then  you can amend.  But if you were under 19 (or under 24 and a full time student)  you don't have to live with them to be a dependent.  Does a dependent have to live with you?
https://ttlc.intuit.com/turbotax-support/en-us/help-article/taxation/dependent-2021-live/L0n7tISmk_U...