In my database I have a table for 'User' who has a foreign key constraint to a 'Servant', who has again a foreign key constraint to a 'Person'.

The relationship between 'Servant' and 'Person' is now changed to an inheritance, so that 'Person' is the base class of 'Servant'.
In this case NHibernate does not care about the 'Servant' ID anymore and only uses the 'Person' ID.

The only problem I have encountered is the foreign key for the servant in the table 'User' now.
Because 'Servant' and 'User' ID did not have to be equal in the past, this is now a huge problem, as NHibernate tries to fetch the 'Servant' of the User by using the 'Servant' ID and looking for it in the 'Person' table.

Is there any solution to this problem to let NHibernate still know about the 'Servant' ID?
The absolute last thing I want to do is to change anything in the database.