So some thoughts:
You say you want to bring attention to the challenges of young people with disabilities, but what attention? Are you talking about people that grew up with disabilities or those that suddenly gain them? And what level of debilitation?

What is your goal behind bringing this attention? Societal change? Policy change?

As many of the people have mentioned, focusing on a single disability might be good... but my thought would be that you can also narrow the focus by choosing what/how/when the disability occurred and it's overall effect on life.

For example; I became disabled in my mid-30's. In just a few months, I went from a highly active professional who also taught Tai Chi and college on the side to a complete life change. At the end of those couple months, I had chronic pain from fibromyalgia and epilepsy.
I have overcome; even though I have had to change so much about my lifestyle. My disability is generally invisible. People don't see me as disabled, because when I am doing well enough to be out and about, I am strong as an ox, bright, and generally in a good mood.

If you are trying to bring attention to the fact of young people suddenly becoming disabled and how it affected their lifestyles and family, then that could be your narrow focus. It then doesn't matter if it was a car wreck, disease, etc... it is the fact that they had this life changing event.
And I wouldn't limit it to 6 female and 6 male. Like some other people mentioned: not everyone is CIS.
I had a hard time finding life insurance after getting fibro, because the vast majority of men who get fibro commit suicide within just a few years, due to a mix of factors. The gay guys tend to fare better than the straight ones in that regard (what with expectations that a man be the bread winner, etc..)
And that being said: if your goal is to bring attention to this challenge, DON'T make it a "feel good" book. Include some of the failure stories. The US disability system has issues, I know from talking on forums with my Brit friends that the UK system for men with invisible illness is much worse. And if you can get permission, interviews with family, friends, etc... of those that ended it in suicide, particularly pointing out the issues that they faced that led to it. Not just: they hurt, but they couldn't get disability, couldn't work, couldn't get proper care, painkiller addictions (especially given that so many doctors just suddenly cut all opioids from patients without regard to the fact that some of those patients really did need the painkillers), etc... or even survivors of attempted suicide.