Heritage

Hi everyone. Im having a problem with heritage. The situation is the following:
I have two tables, tbl_everyone and tbl_employees. tbl_employees
inherits from tbl_everyone.
In tbl_everyone, i store some information about everyone who is
related with the place where i work: Name, ID (PK), Birth Date,
Adress...
Then, in tbl_employees i have aditional information, like area, position, etc.
The problem appears when i have someone in tbl_everyone that becomes
an employee. What do i have to do ? Consider that ID in tbl_everyone
is used in auxiliar tables, so i cannot easily delete the person in
tbl_everyone and insert it again in tbl_employees...
Thanks in advance
Sebastian Davancens