If the parent or parents are able to manage themselves perfectly fine without the child being a hindering problem, then the parent or parents have the right to adopt that child (some tests may be given.)
If you are very disabled.
Not simply because he becomes disabled. There would need to be some other reason for him to lose his rights.
Yes because they are still their parents
yes
yes because disabled people have the same rights as everyone else
An Autistic teen has the same rights as a neurotypical teen. Depending on where you live you also have disability rights, these are not extra rights but rights to protect disabled people.
Yes but they may be too disabled to supervise them so visits may have to be supervised.
The Civil Rights act of 1968
The equal rights of the disabled.
No. Even if they are not his biological parents they still have a parents rights which is more then a siblings rights.
If the child was adopted the grand parents have no rights. It would be up to the adoptive parents whether any relationship could be maintained.
Part of the adoption process involves the termination of rights of the biological parents. When the adoption is finalized, the adoptive parents assume the rights and responsibilities of the biological parents.