Your father will need to file immigrant visa petitions on behalf of his wife and stepchildren. As part of the process, these immigrants will need to demonstrate they will not become public charges. Your father must file an affidavit of support regardless of his income. You may also file an affidavit of support as a joint sponsor. You will need to file Form I-864. You should make sure your income and/or assets meet the Form I-864P requirements. You can read more at http://myattorneyusa.com/overcoming-presumption-of-public-charge.
Answered on Apr 21st, 2016 at 2:46 PM