From much reading of the Posts on this site, Manila has a problem with "Co-Sponsors" in many cases they reject, and expect the petitioner to be the solo sponsor.
QUOTE
k. EVIDENCE OF SUPPORT.
You should be able to demonstrate that you will not become a public charge or be a burden on the U.S. taxpayers for financial support. Submit your petitioners most recent U.S. Federal income tax return (Form 1040) and wage statements (Form W-2). Employment letters stating salaries and bank statements may be included. A completed I-134 Affidavit of Support Form will be useful to the consular officer to evaluate your petitioner's ability to be financially responsible for you.
http://manila.usembassy.gov/wwwfivk1.pdfNothing about a "Co-Sponsor"
Now, if the petition is for a CR-1 or IR-1 spousal visa, they do accept a Joint-Sponsor, because I-864 allows for Joint sponsors.