Under the Hindu Marriage Act, 1955, a child with one Hindu parent is considered Hindu if:

Under Explanation (b) to section 2(1), a child "one of whose parents is a Hindu, Buddhist, Jaina or Sikh by religion and who is brought up as a member of the tribe, community, group or family to which such parent belongs or belonged" is a Hindu. Upbringing decides, not which parent is a Hindu, a court declaration or a later choice.