Catherine Rohland spoke Wednesday for the entire family of the late Donna Muller and her 22-year-old son Richard.
"Our hearts ache for answers that we fear will never come," Rohland said.
The mother and son were shot execution style back in January inside their Lawncrest home.
Police say no valuables were taken and there were no signs of forced entry.
The family dog didn't attack the killer or even bark, according to police
Authorities are asking the public for anonymous tip calls on possible suspects.
"No good lead right now. We've gotten several tips, but I'm letting the public know we need more tips because a lot of them have actually fizzled out," Philadelphia Police Captain James Clark said.
"These were decent, honest, hardworking people. They were both so kind and generous. They were the type of people who would do anything for their family and friends," Donna's daughter Heather Muller Kunf said.
A total of $40,000 in reward money has been posted by the City of Philadelphia for information leading the arrest and conviction of the killer.
"This neighborhood needs to regain some sense of peace, safety, and security," Kunf said.
"We do not know why someone chose to murder them. What is certain is that Donna and Richard Muller should not be dead. They were not violent people," Rohland said.
Anyone with information is asked to contact Philadelphia Police at 215-686-TIPS (8477), text a tip to PPD TIP (773847) or through PhillyPolice.com.