HUSSEIN SAYED, a local anchor with CNBC, a TV network, beams from the stage as he welcomes participants to a conference on family offices (FOs) in Dubai. Among those present are billionaires and their offspring, advisers and money managers, and a smattering of investment-minded blue-bloods, including Prince Michael of Yugoslavia. “We think there may be over $2trn represented in this room,” announces Mr Sayed, “though of course there’s no way of knowing.” Now an essential part of every self-respecting billionaire’s stable, FOs are booming.