The district court also slapped a fine of Rs 5,000 each on them during the hearing yesterday.
Niharika, married to Dhananjay Srivastava, had sustained serious burn injuries under mysterious cicumstances in June 2012. She later died during treatment at a hospital in New Delhi, prosecution said here.
Niharika's brother Neeraj Kumar Sinha lodged an FIR against Dhananjay and his brother Ranjan in this connection.
After hearing the arguments of both the sides, district judge Shailendra Kumar Agarwal held the accused guilty.