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Eugene and Brendan Murtagh

Eugene, 63, chairs Kingspan, a Co Cavan maker of specialised building materials. His 20.7% stake in the London-quoted company has leapt to £461m. He owns The Hempel, a London hotel, and has made £50m in share sales. Brendan, 60, his brother and also a director, saw his 4.4% of Kingspan rise to £98m. He has a Smart Telecom stake and other assets.