Four brothers, Srichand, Gopichand, Prakash and Ashok, together control the Hinduja Group, a multinational conglomerate with a presence in 37 countries and businesses as diverse as trucks and lubricants to banking and healthcare. In India, they are best known for IndusInd Bank and truckmaker Ashok Leyland. Lubricants arm Gulf Oil, which bought U.S.-based Houghton International for just over $1 billion last year, is preparing to list the combined unit. They recently sold a 49% stake in Saudi-based lubricants maker Petromin for over $300 million. Brothers bought and restored the 67,000 sq. foot Carlton House Terrace, a heritage mansion in London, which sits on the site of a former palace near Buckingham Palace; now valued at an estimated $500 million.