Complete aside, I hope that this happens via the demographic collapse and not due to resource/environmental blow back. It would be the smoothest path down. In the same way that inflation is a smoother way to grow a pool of poverty.
The problem is, there isn't _going_ to be a population collapse in developed countries. The path these governments have chosen is to import anyone and everyone in order to keep the numbers growing. Why? Because all those wonderful social programs collapse without people at the bottom of the pyramid to keep things going. The main problem is there's only so many net contributors that can be imported, so we're really scraping the bottom of the barrel for people to bring in and oh yeah, they're eligible for social programs from day one. It's going to be a disaster long term, but it's the future we chose -- "I don't want kids, but I don't want the systems that are in place to collapse either, so sure, bring in the entire world, I'm sure we'll be fine."
Anyone who drives risks their life more than they risk having a special needs child at reasonably non-late age.
We just brush off most such gambles because:
1. People have a terrible intuition for probabilities.
2. If it were better, they would go insane.
Also the entirety of society including their families emphasizing the importance of higher education, good careers, etc. even as the latter is harder to achieve and the former becomes increasingly devalued, yet pricy.
I could live with the 2% chance at 42, but not with the 15% at 45.
Where the chance is of random abnormalities. Who knows what exciting variant you get.
My mother later ended up back in a classroom for a period of time with severely handicapped children. Bound to beds and wheelchairs, non verbal, never going to have independence.
For years after she left her admin job she would go back and spend an evening or two every year watching the kids, so the parents could have some sense of "normalcy".
Her lament was what would the outcome be for these children. Because every one thinks they are doing the best for them by keeping them at home, and close. But the reality is (in so many cases) that the plans for "family to take care of them" almost never works out. Years later my neighbor was an older woman, with an adult special needs child. She died, suddenly, from breast cancer. The brother, who was to take care of him, shipped him off to a group home (because he had kids of his own and lacked the time to care for him properly). That poor mans trauma was doubled when his living situation and life and loss of mother all happened in such a short period.
My own family, I have a severely handicapped cousin (who, became that after a high fever). He too is wheelchair bound and non verbal. However his mother, heeded my mother's advice and transitioned him into a group home early. It worked out well for him as he had a more fulfilling life, and the family (sister, aunts) weren't under pressure for his care, rather just rounding out his life. He still gets out a few times a week with them, and is always around for the holidays.
It's a tough thing for parents to understand that what's best for your special needs kid is sometimes going to be harder on them than all the hard work they doing. And I remain grateful that is isn't a choice I ever had to make myself.
Not referring to your cousin specifically but my mom's life's work is with severely autistic children (the "can't talk and hits people" sort, not "I'm a bit awkward and love math and doing anything to help autistic kids is abject cruelty!" sort), and the experience for parents mostly seems to be abject misery.