My fiance and her 2 children live with and I was wondering if I could claim them as dependents? Her oldest turned 18 in July and her youngest is 11.

If you are not blood related  or married to the mother then you could claim them as "Qualifying Relative" if they qualify  but only if they lived with you all year AND the mother is not required to file her own tax return.  

*** for 2021 only ... the best you can get for them is a non refundable $1000 credit but the mother(even if she didn't work) would get $3000 for the youngest child ... she should file to get the credit. 

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

• No age limit for permanently and totally disabled children

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

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 $4300  (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.

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