The bodies of Tasmin Bahar and Dave Pillay were discovered inside the bathroom of the house in Smithfield of Sydney, Australia.
Bahar had recently separated from her partner of six years, Pillay, and moved out of their Smithfield home, which they shared with their young daughter.
The bodies were found allegedly by Pillay's brother, with the couple's three-year-old child found sleeping in another room in the house.
It's believed Pillay lured Tasmin to the couple's formerly shared home for Father's Day, saying he wanted to see his young daughter, The Age reported.
"We told her not to go to the Smithfield house but she went for Father's Day," Sharagin Bahar, Tasmin's sister, was quoted as saying.
Their cousin, Sifat Sharmin Ruponty, told the Sydney Morning Herald that Tasmin had also told her about being physically threatened by Pillay, with a knife, when they were together.
Sharagin Bahar told The Age from New York that she was in utter shock at the sudden death of her sister, and was flying to Bangladesh and then on to Sydney, hoping to take custody of her niece, who had now lost both of her parents.
"I am so lost. I just want to take my niece into my custody, I want her with me. I'll take care of her. I'll do whatever is best for her," she said.
Tasmin moved to Australia in 2009 and was highly educated, having studied science at university. Police said no other people were wanted over the deaths and the investigation was ongoing.
