I recently read this word online but did not know it’s meaning. As a genealogist, I am a bit ashamed that I did not know the meaning of the word.
According to Dictionary.com:
grandfamily
[ grand-fam-uh-lee, fam-lee ]SHOW IPA
nounplural grand·fam·i·lies.
a family in which one or more children live with and are raised by their grandparent or grandparents: Grandfamilies exist because of absent parents, and the circumstances behind that can vary greatly from one case to the next.