dependants

Not sure what you need to fix ... if he is a qualifying dependent then you did it correctly. 

WHO CAN I CLAIM AS A DEPENDENT?

You can claim a child, relative, friend, fiance (etc.) as a dependent on your 2020 taxes as long as they meet the following requirements:

Qualifying child

•They are related to you.

•They cannot be claimed as a dependent by someone else.

•They are a U.S. citizen, resident alien, national, or a Canadian or   Mexican resident.

•They are not filing a joint return with their spouse

•They live with you for more than half the year (exceptions apply).

•They are under the age of 19 (or 24 for full-time students).

• No age limit for permanently and totally disabled children

Qualifying relative

•They don't have to be related to you (despite the name).

•They cannot be claimed as a dependent by someone else.

•They are a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.

•They are not filing a joint return with their spouse.

•They lived with you the entire year.

•They made less than $4350  (not counting Social Security)

•You provided more than half of their financial support. More info

When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them.

Unemployment compensation is taxable income and counts for the $4000 limit (actually $4300).  So, if he had more than $4300 total income (and is not a full time student under 24) he does not qualify as your dependent.

If you already filed, claiming him, you will have to file an amended return to unclaim him (and pay back as much as $500).  You cannot file an amended return until your original return has been fully processed (you receive your refund).