Sorry if he made over 4,300 you can not claim him. Unless he was under 19 or under 24 and a full time student.
Agreed. If your brother-in-law grosses over $4300, he is not your dependent in 2020.
Age does not matter. The age 19 and 24 rules apply to determining a Qualifying Child.
A sibling can be a qualifying child. See Pub 501 page 12
Agreed. I was just concerned that a Brother-in-law is not necessarily a sibling of the husband and wife he is living with. I should have been more clear. Thanks!
So, yes, if the Brother-in-law is a brother of the husband or wife, then he could be a dependent based on age.
Yes, as long as all of the qualifications are all met for your brother-in-law as a dependent.