Successful serial aviation investor Declan and his younger brother Shane inherited the stake owned by their father, the late Tony Ryan, in Ryanair, the airline that he co-founded. Most of it had been cashed in since the IPO in 1990, however.
But there have been other investments in low-cost airlines around the globe that have notched up many tens of millions in wealth. From Tiger Airways in Asia to Allegiant Air in the US and VivaAerobus in Mexico, and today Viva Air in Colombia and Peru - which may expand in the future to Ecuador and Argentina - Declan's investments are thought to be worth north of €450m.
There was a €42m payday from VivaAerobus in 2017, while a 49pc stake in Irelandia Investments, in which Shane has a stake, and through which the airline investments are made, was said to bring in about €226m in 2016. Declan has revealed that he's aiming to float Viva Air in the US and Colombia next year, and that's likely to bring a further windfall.
Shane breeds horses and owns several vast properties in Kentucky and Tipperary - where he lives on the restored Kilboy Estate - as well as the 600-acre Lyons Demesne in Kildare. In 2017, he got permission to renovate a property on Dublin's Ailesbury Road that previously housed the French Embassy. Planned additions included a gym, swimming pool and five-car garage.
Enniskerry, Co Wicklow-based Declan, meanwhile, has property interests that extend to Poland, Asia, Mexico and Britain, as well as commercial property investments in Dublin. He has backed a number of startups including Coindrum and Igloo Glass, while the brothers also own a stake in Tipperary Crystal. There are also investments in software and biotechnology, and investments through venture capital funds.
A trust founded in the memory of their father Tony was in the process of being wound up last year, having given over €15m to good causes including Barnardos, DCU and Social Entrepreneurs Ireland. Over the years, Declan also made philanthropic donations through his One Foundation, and he is also on the board of FoodCloud, which redistributes leftover food from businesses and supermarkets.