I have added some units to the uses part of my parent TForm.
Then I went to File > New... and created a form inhering my form which has the usages.
The child form seems not to have access to the units used in the parent form.
Is this the correct behavior or is it possible to inherit the uses?
This behaviour is correct. The units listed in a uses clause are made available to that unit only.
If your other unit, containing he derived class, requires symbols from other units, it must list those units in its own uses clause.