Due to a new law introduced in Chile, anyone over the age of 18 years of age or older may now apply for citizenship. The old regulations restricted applications for citizenship to people over 21 years old. All other requirements for citizenship still apply. 

Any person responsible for the legal “personal care” of a child (not to be confused with legal or physical guardianship), may apply for citizenship in Chile for a Child, if the Child is over 14 years of age. By default in Chile, both biological parents have the legal status of responsibility for the “personal care” of their biological Children; unless modified by a court or some other law.

Please see related articles below:

Immigration Visas and Citizenship in Chile:
https://www.spencerglobal.com/chile-immigration-and-visas.html

Child Custody in Chile:
https://www.spencerglobal.com/family-law/24-chile-child-custody-laws.html