I am not sure what you can do friend,
the reality of it is the older you get the less odds of you getting adopted by anyone other then the state its self unless you go independent and have a go on life on your own, the only (most likely) way you will have a family once your past 16 is basically to become independent and find your self a girl and build your self a nest egg and start your own family and life,
most people do not want to adopt someone thats becoming an adult in body,
and most people just can not afford the time and resources for one.
I am sorry, sometimes life really sucks.
its best you try and put your mind and heart and energy into bettering your self and becoming independent enough to start your own life and nest egg in life so that someday someone will take notice and want to share their life and love with you together.
if you remain with the state for the rest of your life you will never gain the type of family your wanting and/or needing.
if your younger then 16, keep trying, perhaps life and fate will give you a much needed brake.
I know how you feel in a since that at one time in my life (err, most of my life) I hated seeing couples and their life because I never had the experience, no hugs, no kisses, no holding of hands, eventually I did, but I had to work hard for it and still do, but that was dealing with relationships and matters of love\sex\mating, etc, not parental,
I had a family (mother/father/2 older brothers and a younger sister) so I can not actually make an honest comparison to the emptiness you must feel inside. I am sorry, I really do wish I could help.
if your permanently disabled, yet able to function in society by your self and for the most part independently and living in the USA, then the state should provide you with enough of an income to help support you enough for you to live an independent life, and they will help you find a home and get started, there in you may be able to find someone like your self to share the rent and responsibility's with together that may in time work out to become a kind of a family together with you, and if that person does not work out then think of it as a kind of practice run for the next person you would like to try with, you must learn to socialize to build relationships, and sometimes that takes allot of work and practice.