“All happy families are alike; each unhappy family is unhappy in its own way.” Tolstoy’s opening lines to Anna Karenina apply equally to family businesses, and no wonder. Add the volatile variables of companies to the multiple maladjustments of most families and you have a potent mix.

It would be hard for fiction to match, for instance, the saga of the Redstones, and their media companies Viacom and CBS. There is the patriarch Sumner, once an all-powerful mogul, now a frail 96-year-old, whose will to cling on to power was literally forged in fire, after he survived a hotel inferno by hanging from a window as flames ate into his flesh. And there is Shari, his daughter, often ignored and belittled, whose influence over the companies has waxed and waned in tune with her relationship with her ageing father — and Sumner’s own relationships with carers and girlfriends.

Last week, Ms Redstone won through, when CBS and Viacom agreed to her longstanding plan to merge the companies, separated by Mr Redstone 14 years ago.