A subject that needs some validation, I am aware that it is not uncommon for Hindus to also pray to Guru Nanakji, which I take as a huge compliment, but given the myriad of deities that Hindus have available to them, it does not seem unreasonable for a Hindu to do this.
The Hindu Marriage Act , 1955 - Section 2
Application of Act.- (1) This Act applies -
(a) to any person who is a Hindu by religion in any of its forms or developments, including a Virashaiva, a Lingayat or a follower of the Brahmo, Prarthana or Arya Samam,
(b) to any person who is a Buddhist...