Can a great-grandchild qualify for benefits on a great-grandparent's account?

GGC's mother died at age 18 (suicide); no acknowledged father -- mother refused to name one on birth certificate, and purported father disavows that he was father because mother was involved with other partners at the time. GGC is being raised by her maternal grandmother (GM), who may not have enough credits and is too young to file for retirement benefits (age 49), and her maternal grandmother's father (GGF - age 82) who is retired and receives Social Security. Both are applying for co-guardianship; no adoption prospects at this time. Can GGD qualify for benefits on GGF's record? or is adoption required? Can she qualify for benefits on GM's record?
Thanks,

Hi,

No, not unless the great-grandchild is adopted by the great-grandparent (https://secure.ssa.gov/apps10/poms.nsf/lnx/0200306235).

Best, Jerry