The attack ad on Paul Gosar, the Republican governor of Arizona, by six of his own siblings could be a career-ending betrayal. But even measured brotherly or sisterly criticism can cast your character into doubt

I can describe it to you, but you have to watch it: there’s an attack ad out on the Republican governor of Arizona, Paul Gosar. His record on everything, from healthcare to jobs to the environment, is poor. He is “absolutely not working for his district”. Voters should “hold him to account”. The visuals are unremarkable: non-celebrity middle-aged people endorsing his opponent, David Brill.

When these talking heads reveal their identities – Joan, Jennifer, Tim, David, Grace and Gaston Gosar, siblings of Paul – the impact is devastating. It sends a thrill up your spine of such raw emotion that you can’t tell for a moment whether your heart has been warmed or frozen. It’s the latter: Gosar’s character has been obliterated. One sibling would be a flesh wound, even three could be managed; six full siblings – unless he has another 10 on call who would challenge them to a mud wrestle – is a career-ending betrayal.

This was a straight jugular-attack, but even to be opposed, maturely, at the level of the idea, by a brother casts your character into doubt: the battle of the Milibands haunted Ed during his leadership, but it also critically weakened David. The natural order of siblings is that, once one wants something, the other steps aside, and does it so graciously that you could never even guess they wanted it: this goes for everything, from a Nobel prize to a life partner. It is laid down by the blood, sweat and tears of toddlerhood, over the bonnet of a plastic truck. If you can’t abide by that, there’s something wrong with both of you; one must be treacherous and the other limp.

There are ways to inhabit the same territory: the Corbyn brothers, Jeremy and Piers, appeared to be on the same turf (the contrarian outlier), but Piers is a denier of anthropogenic climate change, and is doing his younger sibling the tremendous service of making him seem comparatively level and mainstream (see also, Christopher and Peter Hitchens).

It can work intermittently (the Williams sisters), and it may never be as good as the best (the Brownlee brothers), but the craft and effort that goes into professional proximity between siblings surpasses that of the longest marriage.