Greetings Ajay!

Hope you're doing great.

Please, be specific while asking the question. I assume you're asking about marriage candidate eligibility criteria. However, if you've asked with regard to something else please, do ask in the comment section. As per the eligibility and guidelines of UPSC. A candidate must be unmarried at the time of joining the National Defence Academy(NDA).

Similarly, in case you're option Air Force Academy after clearing CDSE examination, the candidate must be between 21-23 years old and should be unmarried.

Hope things are clear now.

Cheers!