The deceased are Anwar Hossain, 27, of Takia Kadma Uttarpara village, his wife Farida, 22, and his mother Phulkhatun Begum, 47.
Warehouse Inspector Ataur Rahman of Mirzapur Fire Service said the boat carrying the three and eight others capsized in the Konai River around 11pm on Friday.
All but the three had managed to swim ashore. The bodies were recovered between Friday night and Saturday morning.