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 part

I have to put the medicines that he needs. In order to do that I found this

but when I press the next button … nothing appears.

Someone has tried multistep with nested forms?

Thanks in advance