The accident took place when four members of a same family, who were heading towards Sangareddy from Jogipet on a motorbike, were hit by a goods lorry near Shivampet village.
Narsamma (30), and her two children - Pavan (10) and Sangamesh (14) - died on the spot. Srinivas, who was driving the motorcycle, was seriously injured and has been admitted to a local hospital, they said.
The lorry driver has been taken into custody.