Nested form


I was trying this cast

and it works but I have to do something else,
I have to do a sort of hospital application, and in the first form I
have to
put the child data then information about his parents and in the last
I have to put the medicines that he needs. In order to do that I found

but when I press the next button … nothing appears.
Someone has tried multistep with nested forms?

Thanks in advance