A 57-year-old man from Chandigarh set a fire that killed his pregnant daughter, her husband and the couple’s 3-year-old son because he was furious his son-in-law came from a lower caste and had not asked permission to marry his daughter, prosecutors in Illinois said on Tuesday.

Subhash Chander, a resident of Chicago suburb Oak Forest, was charged on Monday night with three counts of first-degree murder and one count of intentional homicide of an unborn child in the fire.

In a hearing at the Markham courthouse on Tuesday morning, Chander was ordered held without bond.

Prosecutors identified the victims as 22-year-old Monika Rani, her 36-year-old husband, Rajesh Kumar, and their 3-year-old son, Vansh. Monika Rani was five months pregnant. The medical examiner’s office said the victims died of carbon-monoxide poisoning and smoke and soot inhalation.

Prosecutors allege Chander told them he killed the family because he was upset Kumar belonged to a lower caste. Cook county first assistant state’s attorney Robert Milan told the court, “His son-in-law was beneath him in his opinion.”

Chander’s sister Kamla Devi denied caste was a factor. She told a local radio station her brother was innocent. “There was no family problem. There was nothing going on. Absolutely nothing,” Devi said.

Prosecutors allege Chander used gasoline to start the fire late Saturday. Witnesses were reported as saying they saw two men pouring the fuel in the hallway outside the Aroras’ apartment before the fire was ignited. Illinois state police said tests had matched the gasoline at the crime scene to that found on the clothes of the two suspects.

Arora worked as a cashier at gas stations in the area. The apartment complex in which the family died was inhabited largely by immigrants from India and reportedly owned by an Indian-American.