Immigration authorities say they do not know how many children have been deported because their parents did not have residence when they were born.
Eighteen-year-old Daman Kumar's case highlighted that anyone born after 2006 in New Zealand does not get automatic citizenship.
Kumar was told to leave the country by Tuesday or face a deportation order to India - a country he has never stepped foot in.
Associate Immigration Minister Chris Penk said on Monday he would reconsider the teenager's case, which his office initially turned down in December.
Immigration NZ said it did not hold data on the number of children born to parents who had overstayed their visa since 2006, nor the number of overstaying adults.
The last estimate of overstayer numbers was eight years ago.
"Children born in New Zealand after 1 January, 2006 automatically hold the most favourable visa status of their parents," said Immigration investigations and compliance manager Steve Watson.
"Therefore, if the parents of a child born after 1 January, 2006 are unlawfully in New Zealand, the child will inherit their immigration status as being unlawfully in New Zealand.
"We are only able to estimate of the number of people in New Zealand who may have overstayed their visa. However, this data is limited as it is influenced by several factors including visa validity, historical data entry issues and missing and inaccurate border movements or both.
"This estimate is not broken down into how many of these people are children, or children born after 1 January, 2006."
Penk said any potential amendments to the 2006 law change would need to be discussed by the coalition first.
"My delegation is to consider whether an individual case might have particular circumstances that would merit discretion being applied outside the current rules or policy," he told RNZ.
"So that's what I'll do in this case when I've had an opportunity to be briefed on that."