Sara Sharif was found dead with extensive injuries at her home in Woking on the southern outskirts of London on August 10.
British police identified her father, Urfan Sharif; his wife, Beinash Batool; and his brother, Faisal Malik; as people they wanted to speak to in the investigation.
The three flew to Pakistan on August 9, with the couple going into hiding in central Pakistan and police launching a manhunt.
Sialkot police spokesperson Khan Mudassir confirmed the arrests on Wednesday.
He said the three were handed over to the Federal Investigation Agency, which flew them to Britain from Sialkot in eastern Punjab province. He gave no further details.
An autopsy of the girl didn't establish a cause of death but showed that she had suffered "multiple and extensive injuries, which are likely to have been caused over a sustained and extended period of time", British police said in an earlier statement.
The girl's five siblings, ranging in age from 1 to 13, were recovered by Pakistan police on Monday evening from Urfan Sharif's family home in central Pakistan.
A court ordered the children to be placed in the custody of the Child Protection Bureau in Rawalpindi city, close to Islamabad.
Police had detained 10 relatives of Urfan Sharif, including his father, brothers and cousins, for interrogation in an attempt to pressure the couple to surrender.
