Legislation has been will be introduced on Monday to help implement changes to royal succession laws.
The British parliament is to change the monarchy's 300-year-old legislation that determines who can become king or queen.
Aside from the United Kingdom, New Zealand is the only Commonwealth country that includes the laws of succession in its domestic laws.
The change will apply to the child of their Royal Highnesses the Duke and Duchess of Cambridge, William and Catherine, due to be born in July this year.
The new rules also allow a person married to a Roman Catholic to become king or queen, but the changes will not allow a Catholic to accede to the throne.
