You do not mention how long he has lived with you.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, or fiancé (etc.) as a dependent on your 2024 taxes as long as they meet the following requirements:
Qualifying child
Qualifying relative
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.
To claim a grandchild as your dependent
When you enter the child’s name in My Info, you will be asked “What’s your relationship to [child’s name]?”
Choose “another person”
a drop down menu will appear that lets you choose grandchild
You do not mention how long he has lived with you.
IRS interview to help determine who can be claimed:
https://www.irs.gov/help/ita/who-can-i-claim-as-a-dependent
WHO CAN I CLAIM AS A DEPENDENT?
You can claim a child, relative, friend, or fiancé (etc.) as a dependent on your 2024 taxes as long as they meet the following requirements:
Qualifying child
Qualifying relative
When you add someone as a dependent, we'll ask a series of questions to make sure you can claim them. There may be other tax benefits you can get when you claim a dependent.
To claim a grandchild as your dependent
When you enter the child’s name in My Info, you will be asked “What’s your relationship to [child’s name]?”
Choose “another person”
a drop down menu will appear that lets you choose grandchild