Hello aspirant

hope you are doing well and safe. With reference to your query,  I would glad inform you that for getting eligible for nda entrance exam you must  be atleast 17years of age and have passed 10+2or(wating with 12th results) .Both the student can join nda coaching with no worries. I would advise you to wait for the right time and till then study hard for the exam to crack it in first attempt only

Hope you found this answer informative. Best wishes for your future