It is genetic so of course it is more prevalent in certain families. Autistic people tend to connect with other autistic people so many autistic people have children together. The associated genes are also highly correlated with intelligence and intelligent people tend to be attracted to each other and socialise/ work with others who share their interests which again increases the likelihood of marriages between autistic people and the genes being passed on, compared to generations ago when people generally chose from a much smaller pool of potential partners in their local area. Then of course you have far better research and diagnosis now than even a couple of decades ago so many people would have gone through life previously being unaware that they are autistic - which can be turturous, so thankfully now many more of those who are autistic are actually diagnosed.
I spoke to a geneticist about this when my children were very small and they stated that with two parents with neurodiversity our children were highly likely to carry these genes. They also pointed out that the genes would not have become so widespread if they were not beneficial to society. To flourish society needs dandelions and orchids and effectively these genes are like a highly-leveraged evolutionary bet.
Research shows, for example, that positive childhood experiences have an outsized positive impact on autistic children compared to the population average. But so do negative ones: adverse childhood experiences have an outsized impact on autistic children. In effect it is a magnifying glass, which is why it is so imperative for the whole population that we ensure appropriate support and schools are in place (currently, they are not: 85% of children with poor attendance or out of school entirely are autistic, but the Government refuses to acknowledge this systemic failing to provide adequate and suitable educations environments for autistic choldren).
Many neurodiverse children will become some of our most successful, innovative, productive people if they are given the right support (hence so many successful and important scientists, artists, mathematicians, inventors, composers, entrepreneurs etc being autistic or having ADHD, vastly disproportionate to the prevalence of either in the general population). But it they are not, they will generally crash and burn (which is one reason why our prison population has an extremely high prevalence of people with ADHD who did not receive appropriate support in childhood).
Human society needs dandelions which can weather storms, grow back in adverse circumstances, and provide stability. It also needs those who think differently, create new ways of doing things, challenge ideas, but this comes at a huge personal cost in many cases like when society wants to take the upside of this and yet not provide the right support to protect those who are more fragile. Orchids need more nurture and can’t thrive in any environment. They won’t grow back if stamped on. But if they are nurtured they can flourish into something very beautiful.
I hope we are gradually moving towards people understanding this - for which there is now quite a lot of genetic evidence - rather than focusing only on the downsides to the overall population and not the upsides which the non-autistic population often fail to recognise or acknowledge, portraying autistic people as a burden when they would not have half of the comforts of modern life if autistic people didn’t exist.
It’s an interesting thought experiment to consider what society might be like if autistic people were the majority and it was designed around their preferences and needs rather than the other way around. What I find most ironic is that when autistic people spend all day every day accommodating everyone else’s needs and preferences because we know we’re the minority so it’s understandable that the world is not designed for us, the non-autistic population often makes an enormous fuss about the slightest accommodation in return even if it has minimal or no effect on them, and then accuses autistic people of lacking empathy (which has been thoroughly debunked anyway, but people do love their ignorant stereotypes).