Sorry for crossposting.
I posted this to objectpascal group
waited for an week, but no answer.

How to achieve this for old style object types?

type
TParentType = class;  // forward declaration of class
TChildType = class
private
    blah blah
    FOwner: TParentType;
    blah blah
end;

TParentType = class  // real declaration
private
    blah blah
    function GetChild( s_tag: string ): TChildType;
    blah blah
public
    blah blah
    property Child: TChildType read GetChild;
    blah blah
end;

this works fine, but if I replace word "class" with "object"
then compiler complain at first line ( with forward declaration comment )

In manual and help there is nothing about old style objects
beside advice not to use them.

I looked in Turbo Pascal 5.5 object programming guide but nothing there also.