无效的非静态成员，，，求大神 求解

#include<iostream>
#include<string>
using namespace std;
struct PersonData
{
    string name;
    PersonData*child;
    PersonData*bor;
};
class FamilyTree
{
public:
    FamilyTree()
    {
        Ancestor=new PersonData;
        cout<<"请输入祖先的名字\n";
        cin>>Ancestor->name;
    }
    void CreatPerson(PersonData*person=Ancestor);
    bool Getinfo(PersonData*);
    void disPlay(PersonData*person=Ancestor);//输出全部成员信息
public:
    PersonData*Ancestor;
};
编译出现“error: invalid use of non-static data member 'FamilyTree::Ancestor'|”的错误，，不知道怎么搞的，，，