Two men have been arrested in connection with the murder the Birmingham couple Avtar and Carole Kolar, the parents of a police officer.
The couple,aged 62 and 58, were found dead in their home in Handsworth Wood on 11 January, by their son Jason, a detective constable with West Midland Police.
Forensic post mortem examinations confirmed that the couple had been killed by repeated blows to the head.
A 24-year-old man was picked up by police who raided his home on 13 January and a 41-year-old was arrested on Sunday morning. The pair were being questioned on suspicion of murder.
Police are continuing to appeal for more information.
"This was a horrendous attack. We continue to follow a number of lines of inquiry," said Det Supt Richard Baker, who is leading the murder investigation.
"We encourage anyone with information to speak to us no matter how insignificant they feel the detail is."
A reward of £10,000 is being offered by Crimestoppers for information that leads to a conviction.
The couple have four children and eight grandchildren. Their daugther, Michelle Kirwan, and son, Avtar Kolar, gave an emotional press conference where they said the family's hearts had been "broken forever".