I vote I864 A since you live in the same household.
Good Luck!
Who May Be Considered a Household Member for Purposes of Form I-864A?
For purposes of this contract, one or more of the following individuals may sign the Form I-864A as a household member if at least 18 years of age:
1. The intending immigrant, if the sponsor seeks to rely on an intending immigrant’s continuing income to establish the sponsor’s ability to support the intending immigrant’s spouse or children;
2. The spouse, parent, child, adult son or daughter, or sibling relative of the sponsor, if that relative has the same principal residence as the sponsor; or
3. Any other individual whom the sponsor has lawfully claimed as a dependent on the sponsor’s most recent Federal income tax return even if that person does not live at the same residence as the sponsor. If more than one individual agrees to help support the sponsored immigrant, each individual must sign a separate Form I-864A.
https://www.uscis.gov/sites/default/files/document/forms/i-864ainstr.pdf