Template-template compiler error with CRTP

Question

(The suggested similar questions do not involve template-templates)

I have a templated inheritance hierarchy to share types and behavior.

Grandparent uses types defined by Parent and calls Parent functions. Parent can call Child functions.

Below is a full code example:

https://godbolt.org/z/aW6PPnazG

template<class CONFIG,
         template<class, template<class> class> class PARENT,
         template<class> class CHILD>
struct GrandParent
{
    using PARENT_T = PARENT<CONFIG, CHILD>;

    GrandParent()
    {
        static_cast<PARENT_T*>(this)->ParentFunc();  // Calls Parent functions
    }

    typename PARENT_T::Component _comp;              // Compiler error. PARENT_T is incomplete
};

template<class CONFIG, template<class> class CHILD>
struct Parent : public GrandParent<CONFIG, Parent, CHILD>
{
    using Component = int;
    using CHILD_T = typename GrandParent<CONFIG, Parent, CHILD>::CHILD_T;

    Parent()
    {
        static_cast<CHILD_T*>(this)->ChildFunc();    // Calls Child functions
    }

    void ParentFunc(){}
};

template<class CONFIG>
struct Child : public Parent<CONFIG, Child>
{
    void ChildFunc(){}
};

struct Config{};

int main() 
{
    Child<Config> c;
    return 0;
}

However, I am struggling because I get a compiler error at the very end that PARENT_ is incomplete when I try to get an alias it defined:

<source>:15:34: error: invalid use of incomplete type 'using PARENT_T = struct Parent<Config, Child>' {aka 'struct Parent<Config, Child>'}
   15 |     typename PARENT_T::Component _comp;
      |                                  ^~~~~
<source>:19:8: note: declaration of 'using PARENT_T = struct Parent<Config, Child>' {aka 'struct Parent<Config, Child>'}
   19 | struct Parent : public GrandParent<CONFIG, Parent, CHILD>

The second compiler error refers to Parent inheriting from Grandparent. However, I was hoping to keep using template-template parameters, up until Grandparent to keep Child and Parent classes simpler (because there are many of them) and push the template complications to Grandparent.

What is the best solution?