Query On Gratuity - Gratuity Applicability

Dear Seniors,
I am seeking your legal openion regarding applicability of gratuty in below case
a person has joined an organization , during his tenure with the organization, he got transfferd 5-6 times in diffrent establishments of the organization without completing 5 years in any of the company, though he has served almost 20 years in the organiztion.
my questeion is ,
wheather he is eligible for gratuity, if yes, what would be the period / tenure of service, if it is 20 years, reqested to please provide the reffrels / judgements
can seniors help me in this issue,

Could you please explain that ?
Under which provision of the act is gratuity payable for being a part of a group ?

Had the person been transferred to differnt locations but working with the same company, he would have been evidently be applicable for gratuity for this long duration.
From your query I believe -
There is a Group M and has 5-6 different companies say A, B, C, D, E, F.
The person was employed by A.
He completed around 4 or so years of service and was transferred to B.
Likewise, he was transferred to C after few years but before 5 years can be completed and this just went on.
Now the thing is in such cases,
Was the person given relieving letter from the pervious company and a fresh appointment letter from the new company?
OR
Was the person given a transfer letter that stated that he is being transferred from A to B (B to C and so forth) and that his tenure with his past companies would be merged with his tenure in new company?
In former case there is no applicability for gratuity.
In the latter case, I think he can be eligible. Though Seniors can advice better here.
Hope it helped.