Rana Haris Ali, nine, got into difficulty in Loch Lomond in southern Scotland, at around 6.40pm on Saturday. He was in the water with mum Edina Olahova, 29, and family friend Mohammad Asim Raza, 41, who both also died.
A seven-year-old boy is currently fighting for his life in intensive care in hospital, Daily Record reports.
The family of Edina and Rana said they were heartbroken after a “tragic drowning accident”.
They described young Rana as a charming and lovely boy.
The statement released to Sky News says: “The family is heartbroken at the death of our charming young boy in what was a tragic drowning accident on Saturday.
“Haris Ali was the loveliest little boy.”
The two families were pictured together just hours before the tragedy as they enjoyed the warm weather near the banks of the loch.
The chief executive of the national park extended his sympathies to friends and family as the tragic weekend was described as “one of the worst” in history.
The deaths are the latest in a string of tragedies in water during the heatwave.
Gordon Watson, Chief Executive of Loch Lomond & The Trossachs National Park Authority, said: “Further to the incident on Friday in which a young man died, another tragic incident has taken place on Loch Lomond over the weekend.
“Our Boat team took part in a multi-agency search operation in the north end of Loch Lomond on Saturday evening led by Police Scotland after a group of people got into difficulty in the water. Tragically, three people, including a child, have lost their lives.
“First and foremost I want to extend my deepest sympathies to the loved ones of those who have died. I also want to thank all of those involved in the search and recovery operations. This has undoubtedly been one of the worst weekends in the National Park’s history.
“We work hard to help people enjoy the waters of the National Park safely and responsibly using a range of measures, including new safety equipment on our sites, clear signage and safety campaigns in the summer months.
“Over the coming days we will, along with our partners, reflect on the events of this weekend and discuss what more can be done by us all to prevent further tragedies in our lochs.”
“A multi-agency operation took place and sadly, three people were pronounced dead at the scene.
“Formal identification has still to take place but the family of a 41-year-old man, 29-year-old woman and nine-year-old boy have been made aware.
“A seven-year-old boy was taken by ambulance to the Royal Hospital for Children in Glasgow and is currently in intensive care.
“A full report will be submitted to the Procurator Fiscal.”