From Work Rights Press – publisher of the most popular union-side labor law handbooks in the United States.
A. Surprisingly, yes. Grandparents are not considered "family members" under the FMLA. But the Act permits an employee to take time off to care for a person for whom the employee stands in loco parentis, meaning “in place of the parent.”
Given your grandmother's infirmities and dependence, you qualify as her parent. This entitles you to take FMLA family-care leave.
For more on this topic, read The FMLA Handbook: A Union Guide to the Family and Medical Leave Act by Robert M. Schwartz. Available for $20 on the Work Rights Press website or available for members at the Local 888 union hall for just $16!