The incident took place yesterday morning and police have arrested Vilas Bhise (58), the father of PSI Vijay Bhise, who is at large, in this connection.
According to an official, the victims were identified as Vijay Yahswant Sul (29) and Sunil Sonwalkar (27).
"Sul had been in a relationship with Vilas' daughter since the last few years. However, Vilas and his son were strongly opposed to their affair as Sul was married," the official added.
"The father-son duo first threw chilli powder in the victims' eyes so that they cannot resist and then assaulted them with a sharp object," the official said.
While Bhise has been arrested, his son, who is a PSI with Mumbai Police, is still at large, he said.
An offence of double murder has been registered with Phaltan Police against the duo, he said.