It was love, rather than duty, that took a good friend of mine to a funeral last week. But it was the kind of love that can be hard to explain. She hadn’t lost a blood relative, or a friend. Instead, the funeral was for the first wife of my friend’s much-married father, a woman for whom – unlike a cousin or a sibling or even a step-parent – there isn’t an official word. But still, she was family, the beloved mother of my friend’s equally beloved older half-sisters, a fixture in all of their long-interwoven lives, even though they had never all lived together under one roof. As always in grief, it isn’t only love for the deceased that brings us together, but love for the living and bereaved. Families are complicated beasts, not always easily packaged into tidy boxes or one-word explanations, but it is those sprawling complications that make us what we are. What matters in the end, as a thoughtful and nuanced report from the children’s commissioner Rachel de Souza made clear this week, isn’t whether your family fits some narrow, approved template but whether they make you feel loved and supported, confident that someone would catch you if you fell. In policymaking, she argues, “too little attention has been paid to the things which families say matter: relationships, trust in one another, love, and time together”, yet these should be taken as seriously as household composition or income. What makes this such an interesting argument is that its author can’t be dismissed by an incoming Conservative administration as a bleeding-heart liberal. De Souza is a steelworker’s daughter from Scunthorpe, the Boris Johnson-appointed former headteacher turned academy trust leader, whose schools were famed for relentlessly driving up standards in deprived neighbourhoods, and she sees happy families not as something fluffy and nice to have, but an important, overlooked driver of social mobility and life prospects. Children who get on well with either of their parents aged 13, she writes, have higher earnings at 25 than those who don’t. Close family relationships are directly correlated with GCSE grades, and for adults, believing you can rely on family in a crisis is associated with higher wellbeing across income groups. Being able to go out into the world confident that someone has your back matters, even if that person doesn’t fit a traditional definition of family. Yet still much of the rightwing press coverage was gloomily hand-wringing, lamenting the shocking breakdown of the nuclear family. True, the report confirms that almost one in four families is headed by a lone parent – although that figure can’t be enormously shocking, given it’s barely changed in 20 years – and 44% of children will not see out their childhood living with both parents, due to separation or bereavement or in some cases being taken into care. Families are also shrinking: the same percentage of parents have one child as have two, although some of those households may expand with time. The cosy old unit of two adults and 2.4 children – the kind plenty of us are reminded we don’t have whenever we buy a four-pack of something from the supermarket, get a “family” ticket for some day out that doesn’t cover our actual families, or duck another nosy question about why we don’t want kids at all – is no longer necessarily the norm. But as the report points out, it’s hard to disentangle the effects on children of their parents splitting up from the effects of whatever misery drove them to split (or indeed from what follows, which can be poverty). What should interest policymakers is why some families seem to survive conflict, change and crisis better than others. For while “blended” second families aren’t always easy, an initially spiky jumble of steps and halves can and miraculously often does eventually reassemble itself into an emotionally rich and happy new life. When de Souza’s team interviewed scores of children and adults to see how they defined the f-word, surprisingly often it wasn’t by DNA; some had friends so close they felt like family, but blood relatives they barely knew, while others spoke movingly about all sorts of formative figures in their lives. The most common word used when asked what family means, meanwhile, was “everything”. Unconventional families aren’t necessarily easy to capture in government statistics, as de Souza points out, or describe to outsiders. When Labour’s deputy leader, Angela Rayner, took bereavement leave last year, she didn’t initially say whom she had lost because she didn’t quite know how to explain the relationship with the woman she calls “her adoptive mum”. The truth was that the woman who took a somewhat lost 20-year-old Rayner under her wing was the unconditionally loving maternal substitute Rayner had leaned on for guidance throughout her adult life, following a difficult childhood as a carer to her own biological mother. “That’s the thing in bereavement, people’s relationships are so complex,” Rayner told me some months later. “Who is your close family? To a lot of people that’s your mum, your dad, your son, your daughter – well it’s not like that for a lot of people.” The pro-family government approach de Souza recommends needs to embrace a sometimes messy, blurry but realistic concept of what it seeks to support. Some will balk at the words “pro-family”, evoking as they do finger-wagging lectures about getting married or rightwing populists offering bribes to breed (even though family life for many means supporting elderly parents, not children). But David Cameron’s initially twee-sounding “family test” – the idea that all domestic policy be scrutinised for its effect on family life, which de Souza wants to review and revive – looks in retrospect like a major missed opportunity for progressive change. When public health experts warn that children will die this winter in cold damp homes, refusing to help the poor with their fuel bills would surely be an instant fail. So would Jacob Rees-Mogg’s obsession with forcing everyone back to the office, a housing crisis that leaves too many thirtysomethings contemplating bringing up kids in tiny rented flats, the exploitation of children’s homes for profit, frighteningly long waits for adolescent mental health services, and a social care system that doesn’t let those exhausted by looking after elderly parents catch a break. If love, time together, trust and a thriving emotional life are the goal, then everyone ought to be able to get behind a pro-family policy. The traditional family is dying? Then long live the happy one, whatever shape it takes. Gaby Hinsliff is a Guardian columnist