According to a complaint lodged by the minor's mother, the accused, identified as Wasil, took her son to a secluded place on Saturday and allegedly sodomised him.
The four, including arrested accused Deepak Passi (20), have been charged with kidnapping and assault, Inspector Sahadev Sahu of Gora Bazar police station said.
The court convicted the couple under section 6 (aggravated penetrative sexual assault) of the Protection of Children from Sexual Offences (POCSO) Act on Thursday and awarded the sentence.
The alleged incident took place on Thursday evening, Ratanpuri Station House Officer (SHO) Vindhyachal Tiwari said.
The agency also arrested a man from Delhi in connection with the case but is keeping his identity under wraps, they said.
The girl's father had lodged a police complaint against the man, following which he was arrested on Sunday, Karvi Station House Officer (SHO) Virendra Tripathi said.
The police stopped a poverty-stricken couple in Nawabpet of Mahbubnagar from selling their 17-year-old daughter to a person in Hyderabad on Friday.
Additional District and Sessions (POCSO) Court Special Judge Pawan Kumar Sharma on Tuesday also imposed a fine of Rs 50,000 each on Lavlesh and Suresh, who are cousins.
The girl's family took her to a doctor on Thursday when she was not feeling well after the incident.
Special judge Bharti Kale on Wednesday found Shiv Kumar alias Shiva Rana guilty of the offence under provisions of the Protection of Children from Sexual Offences (POCSO) Act and IPC.
The charge includes willful neglect as a result of which cruelty was inflicted upon the child.
The matter came to light on Sunday evening when the minor managed to escape from the clutches of the accused after two days and reached her house in Chakeri.
The court subsequently on Thursday extended the arrested engineer's judicial custody till November 30.