C++ program to implement the initialization of Nested Members in a class:

NestedClass.cpp

#include<iostream>

using namespace std;

class first{
    int fa,fb;

    public:
        first();
        first(int x,int y);
        void display();
};

first::first():fa(0),fb(0){
}

first::first(int x,int y):fa(x),fb(y){
}

void first::display(){
    cout<<fa<<" "<<fb;
}

class second{
    first f;
    int sa,sb;

    public:
        second();
        second(int x,int y,int a,int b);
        void display();
};

second::second():f(),sa(0),sb(0){
}

second::second(int x,int y,int a,int b):f(x,y),sa(a),sb(b){
}

void second::display(){
    cout<<"The Numbers are ";
    f.display();
    cout<<" "<<sa<<" "<<sb<<endl;
}

int main()
{
    second obj;
    cout<<"Initially,";
    obj.display();

    int a,b,c,d;
    cout<<"Enter any four numbers.";
    cin>>a>>b>>c>>d;
    second obj2(a,b,c,d);
    cout<<"After,";
    obj2.display();

    return 0;
}