No, the employer should have taken additional steps before denying the leave, according to the Second Circuit in a case with similar facts. Although the employee did not mention it in his leave request, he had an in loco parentis relationship with his grandfather, who had raised him as a child.
The employee was not required, at the time of his request, to provide the employer with all the information it needed to decide with certainty that the leave was covered under the FMLA, the appeals court explained. Rather, the employer was obligated to specify what additional information it needed to determine whether the employee was entitled to such leave.
Both the express provisions in the FMLA for coverage with respect to in loco parentis relationships and the express example of a grandmother in the publication available to employers on the U.S. Department of Labor's website, made it reasonable for the employer to understand that the employee's request for leave in order to take care of his seriously ill grandfather might come within the FMLA.
Source: Coutard v. Municipal Credit Union (2dCir 2017) 167 LC ¶36,505.