Yes. If the ex employee was eligible for Gratuity at the time of leaving the services as per the Gratuity Act, then he is eligible to claim any time, even though 5 years period is elapsed now. Normally any unpaid gratuity, if not claimed, within some reasonable time, the Employer supposed to deposit with The Commissioner, under Payment of Gratuity Act for disposal. Then the claim could be forwarded to him for disposal.
Whereas most of the industries the Gratuity payable is now linked to Life Insurance Corporation of India as per statutory requirement, than the claim can be forwarded for their deposal.