The persons arrested were -- Khatri's father Rajkumar, his elder brother Sandeep, uncle Kishan Kumar and cousin Navin.
In a bizarre manner, Khatri, 23, after murdering her had hid her body at the ventilation shaft of his residence and married another woman during that period.
The four persons have been booked under Sections 201, 202, 203 (related to destruction of evidence and giving false information) and 212 (harbouring offender) of the IPC, DCP (North West) Vijay Singh said.
Later, he also asked them to wash the blood stains on his car, in which he allegedly strangulated Arzoo on February 2 night and carried her body in the trunk, police said.
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Soon, Rajkumar and Sandeep allegedly sought help from Kishan Kumar and Navin.
In fact, it was Navin who took his cousin's car out for servicing on February 4, the day Khatri got married.
However, all of them tried to mislead the police throughout the probe claiming that they had no knowledge about the incident, police said.
They were arrested today and presented in a court.
Meanwhile, a court sent Khatri to 14 days of judicial custody, police said.
The incident came to light on Sunday when the police questioned Khatri regarding Arzoo's abduction, when he confessed to have killed her in south-west Delhi's Nangal Dawat village and later dumped her body in the shaft.
On the same day, the police recovered Arzoo's decomposed body from the shaft and Khatri was arrested.
Both Arzoo and Khatri lived in the Rajpura Gurmandi locality which comes under the jurisdiction of Model Town police station.