Rosemount House in Dundrum is bright and refurbished. For a decade it was the home of Harmonia, Norah Casey’s magazine group. Today, the building houses the LHK Group, one of the country’s oldest Irish-owned insurance brokers. Led by 44-year-old Colm Kelleher, the group is a third-generation family-owned business that was founded by Kelleher’s grandfather Myles in 1938. It is a dynamic business that is resolutely Irish-owned at a time when private equity is hoovering-up Irish-owned brokers at a breakneck pace. Buyers including the Goldman Sachs-backed Aston Lark and Árachas, which is owned by private equity funds HPS Investment Partners and…