You can claim your biological son as a dependent on your 2020 return as long as the following requirements are met:
- He isn't claimed as a dependent by someone else.
- He is a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
- He isn't filing a joint return with his spouse, if applicable.
- He is under the age of 19 (or 24 for full-time students).
- No age limit for permanently and totally disabled children.
- He lived with you for more than half the year (exceptions apply).
- He didn't provide more than half of his own support for the year.
For your non-biological daughter, you can claim her on your 2020 return if the following requirements are met:
- She isn't claimed as a dependent by someone else.
- She is a U.S. citizen, resident alien, national, or a Canadian or Mexican resident.
- She isn't filing a joint return with their spouse, if applicable.
- She lived with you the entire year.
- She made less than $4,300 in 2020.
- You provided more than half of her financial support.