Winslet, 35, and her daughter Mia, 10, were staying in Branson's Necker Island Great House along with more than a dozen other people, including Branson's 90-year-old mother Eve and 29-year-old daughter, Holly, Britain's The Guardian reported.
"Around 20 people were in the house and they all managed to get out and they are all fine," said Branson, who was staying in another Necker Island property 100 yards away with his wife, Joan, and son, Sam, 25.
"We had a bad tropical storm with winds up to 90 mph. A big lightning storm came around 4 a.m. and hit the house. My son Sam rushed to the house and helped get everyone out. The main house is destroyed and the fire is not yet completely out. My office was based in the house and I have lost thousands of photographs, which is very sad," Branson said.
Although the damage was extensive, Branson seemed positive toward its future.
"It's very much the Dunkirk spirit here. We want to rebuild the house as soon as we can. We have a wonderful staff here and we want them to stay in work. We'll all stay here for the time being. There's a lot of damage and we won't be able to stick it back together again right away. It was a beautiful house."