Brothers Greg (57) and Niall Turley (50) made their fortune growing online car hire firm Cartrawler out of Argus Car Hire, their family's business in south Dublin.
The firm has been sold twice, initially in 2011 for €110m and then again in 2014 for €450m. Along the way they've taken some cash off the table, but have managed to hold on to about 25pc. The company employs 600 people around the world and had revenues of €201.7m in 2017.
A third sibling, Mark (52), runs Clonbio, which owns Europe's largest biofuel plant in Hungary, and is backed by a group of US and European banks. It booked a profit of €35.5m in 2017 on revenues of €278m. The Turleys own a majority stake in the business, which has by-products of high protein animal feed, corn oil and a healthy prebiotic bran extract.
The latter has seen a new business formed, PureFiber, of which the brothers will own 80pc with the remainder owned by a number of Swedish investors. Niall owns a castle on 265 acres in Galway, while the three are also believed to own properties in south Dublin. Greg has also backed several tech startups here and in the US.