Can my older sister (33) or brother in law claim me as a dependent (I’m 31)? I’ve been living in their house since late may 2020 and I pay rent and I have two jobs

[chpur398]

I believe that my combined gross income for the two jobs is somewhere around $20,000

[Mike9241]

they can not claim you as a dependent.  your gross income is way too high (can't be over $4,300) 

[Hal_Al]

There are two types of dependents, "Qualifying Children"(QC) and standard ("Qualifying Relative" in IRS parlance even though they don't have to actually be related). There is no income limit for a QC but there is an age limit and student status test, a relationship test and a residence test. Only a QC qualifies a taxpayer for the Earned Income Credit and the Child Tax Credit. 

A person can still be a Qualifying relative dependent, if not a Qualifying Child, if he meets all 6 tests for claiming a dependent (failing any one test disqualifies a dependent):

1. Closely Related OR live with the taxpayer ALL year
2. His/her gross taxable income for the year must be less than $4300 
3. The taxpayer must have provided more than 1/2 his support

In either case:

4. He must be a US citizen or resident of the US, Canada or Mexico
5. He must not file a joint return with his spouse or be claiming a dependent of his own
6. He must not be the qualifying child of another taxpayer