Speedy Trial Tribunal 4 Judge Abdur Rahman Sardar announced the verdict on Tuesday around 12pm.
The convicts – Sayeed Howlader, 30, Sonadanga upazila, Khulna, and Riaz Nagarali, 32, from Muradpur upazila, Comilla – were also fined Tk20,000 each.
According to prosecution, one of the victims, Rowshan Ara Begum, wife of late additional superintendent of police Abdul Kuddus, lived on the first floor of a residential building with her domestic helps Lucky Akter and her 12-year-old daughter Kalpana Akter in Kolapatti area of Jatrabari.
Kalapana's elder brother Sayeed was familiar with the family and used to visit them regularly.
On March 28, 2015, Sayeed and his friend Riaz demanded Tk10,000 from Rowshan as loan. Lucky was not at home at the time.
When Rowshan refused to lend him the money, Sayeed started arguing with her, and at one point he picked up a knife from the table at the house and slit Rowshan's throat with it.
Then Sayeed and Riaz killed Kalpana the same way as she had witnessed them kill Rowshan.
Later, Rowshan's brother Mozammel Hossain filed a murder case with Jatrabari police station.
Police arrested Sayeed in Dhaka's Shahajahanpur area two days after the murder.