What is the best way to deal with co-dependent classes in C++?

Question

Say I have a class foo with an object of class bar as a member

class foo
{
    bar m_bar;
};

Now suppose bar needs to keep track of the foo

Answer 1

As far as I know, the only real way of doing this is using pointers since they don't require class definition until the translation unit (.cpp) in which case both classes will have been defined properly.