inheritance is madness

Hello Gurus

I'm very surprised at the fact that primary keys are not inherited.
When trying to make foreign keys from a third table to a parent table,
the child table's data is not counted [I assume] due to this fact,
even if the child table has the same primary key. This is really
weird, considering a select from the parent table will return the
child table's data. Does anyone know of a hack to get this behavior to
change, and allow the third table to use a foreign key that references
child table data?

Thanks very much,
Travis