As you said, the hxx,ixx,jxx files are generated by wok.
in the hxx, you have your class definition.
If you are using a Handle_Package_Class in your class ( as field for example ), you only need to include Handle_Package_Class.hxx
But in your code, you will need to use the Package_Class object. So the include Package_Object.hxx is automatically included in the .jxx
The file .ixx contains the Handle definitions ( like DownCast, Standarrd_Type, etc.. )
Have a look in the distribution at <>\drv\AIS\AIS_Shape.ixx and <>\drv\AIS\AIS_Shape.jxx
HTH