Winslet, 35, her two children – Mia, 10, and Joe, 7 – and her boyfriend, Louis Dowler, were staying in Branson's $70 million private island home in the British Virgin Islands when it was lost in the inferno.
"Many thanks to Kate Winslet for helping to carry my 90-year mum out of the main house to safety," Branson, 61, blogged Monday.
Lightning struck the house around 4 a.m. as Tropical Storm Irene passed over Necker Island, according to Branson.
"Around 20 people were in the house and they all managed to get out and they are all fine," wrote the Virgin Group CEO, who was staying in the house next door at the time.
"We will rebuild the house as soon as we can," Branson vowed. "We have a wonderful staff here and we want them to stay in work. … There's a lot of damage but we’ll create something even more special out of the ruins."
He added: "Currently just huddled up with family and friends in the continuing tropical storm realising what really matters in life."
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