C++ ::  Passing A Polymorphic Array Entry

I'm having an issue during the linking stage of the .exe during compile time, and it's because of a call to a function with a polymorphic parameter.

//here's how the classes are setup
class grandpa {};
class mom public grandpa{};
class dad public grandpa {};

[Code]....

dad has sons in the vector and mom has daughter in the vector. What I want to do is have a function that can accept either of these vectors as one parameter like so: void func(const grandpa* aObject);

Finally, I have an error when I pass an object to the function like so: func( d[0] );