Need help regarding educational qualification for a railway job.

The furnishing of false information or suppression of any vital factual information to employer may result in your dismissal.

Double graduation is an excellent qualification and if you have applied for a job where 12th class is the entry-level qualification, you can very well disclose that you are holding a Degree also. 

"...I don't want to disclose one of them because of some personal reasons..."

The above statement does not hold any water when it comes to disclosing your qualifications to your would-be employer. Please note that it is not a crime to apply a job to which you are overqualified. If you want the job, please join duly informing everything and be happy. Maybe in the future, there shall be an internal opening like a promotion where if you hold a degree, you get it quicker. Then you shall face a difficult position at which time.  Fair play is always better. 

Generally, law judges any action on the basis of intentions, not mere facts. When you are hiding the reason for the non-disclosure of the qualification, it is impossible ti make any meaningful suggestion.