Family members of citizens of the European Union or of the States of the European Economic Area (EEA) and Switzerland are entitled to a preferential free-of-charge Schengen visa.

The expression “family member of EU citizen” is further used for family members of a citizen of any of the EU countries or Iceland, Lichtenstein, Norway and Switzerland (further only “EU citizen” for the purposes of these provisions), who is a:

• spouse,
• parent of an EU citizen,
• on condition that the EU citizen is under 21 years of age and lives in a common household with the applicant,
• child under 21 of an EU citizen, or such a child of the spouse of an EU citizen
• dependent direct relative in an ascending or descending line of an EU citizen, or such a relative of the spouse of an EU citizen.

Note 1: A dependent person is a third-country national supported by an EU citizen or their spouse who:

• Is systematically preparing for a future profession and is up to 26 years of age;
• Cannot systematically prepare for a future profession or perform gainful activities due to illness or injury;
• Is not capable of performing systematic gainful activities due to a chronic adverse health condition.

Note 2: A family member of an EU citizen can also be a foreign national who can credibly prove that:
They are a relative of an EU citizen not specified above if:

• They lived in a common household with an EU citizen in the country whose citizenship they hold or in the country where they held long-term or permanent residence;
• They are supported by an EU citizen;
• They cannot care for themselves without personal care provided by an EU citizen due to a chronic adverse health condition.
• or s/he is in a permanent relationship with an EU citizen that is comparable to a family relationship and they share a common household.

Special visa procedures for family members of EU citizens
Family members of EU citizens are entitled to:

• Priority appointment to submit the application, should they need an appointment
• Processing the visa application free of charge

Source: https://economictimes.indiatimes.com/nri/visit/you-can-get-a-free-schengen-visa-if-/articleshow/116039237.cms