Staff dual role on group companies - Is it mandatory to include those staff involved in group companies in PF and Gratuity?

Staff Dual role on group companies, Pf and Gratuity part remain in principle company. is it mandatory to include those staff involved in group companies in PF and Gratuity. Please let us know for clarity and clear picture for dual role staff.
Thanks and Regards
P.S. Ranganathan.

In 'group company'there will be lot of financial inter dependency among the companies. When there exists financial inter dependency the PF and other labour authorities can club these different establishments together for coverage of various enactments. Therefore, the employees in group companies shall be covered by Gratuity Act, PF Act and other Labour Acts or certain sections of Act the coverage of such Acts.