To be eligible to sponsor a relative to immigrate to the United States you must meet the following criteria:

You must be a citizen or a lawful permanent resident of the United States and be able to provide documentation proving your status.

You must prove that you can support your relative by providing documentation that your income is at least 125% above the U.S. poverty level for your household size, including all sponsored family members.

If you are a US Citizen you may petition for the following foreign national relatives to immigrate to the United States; however you must be able to provide proof of the relationships:

oHusband or wife;
oUnmarried child under 21 years old;
oUnmarried son or daughter over 21;
oMarried son or daughter of any age;
oBrother or sister, if you are at least 21 years old; or
oParent, if you are at least 21 years old

If you are a lawful permanent resident you may petition for the following foreign national relatives to immigrate to the United States; however you must be able to provide proof of the relationships:
oHusband or wife; or
oUnmarried son or daughter of any age