The incident took place last evening when brothers Joginder Singh (26), Surender (24) and Joginder's wife Seema were working in their field, they said.
As heavy rains started to pour, the three took shelter under a tree where lightning struck them.
The three were taken to Civil hospital in Jind where Joginder and Surender were declared brought dead, police said adding, injured Seema was admitted in a serious condition.