Hi, I’m an aunt to my nephew, and he’s got a son I’m raising from a child, and now he’s seven, can I take custody of him?

I raised my nephew son from the day he left the hospital, he’s seven, and his dad took him back to his mother, and none of them had ever helped this boy, even though his mother had welfare and social security for him, which he had never seen a penny. I ‘m going to have to mention that my nephew is autistic and non-verbal, can I apply for him as an aunt for custody?