Sorry i'm new to blender so i dont know how can i word this question better. I just learned that these dotted lines relationship lines. So i guess they show parent-child relationship between objects but in this case its not what i expected it to be. I have this door here whose relationship line goes to the origin even after i clear its parent (alt+p >> clear right?). even if i set parent of the door the doorframe object which is around it (select door>>then select frame>>ctrl+p>>object), the relationship line from the door still keeps going to the origin. This looks and works ok in blender for some reason but i want to export this model as fbx to unity. In unity, these doors dont show up at all.
As you said you've tried Ctrl+p, so the door is not a child of any object. Then the only thing that can cause this problem is that the origin far away from the door. Select the door, press T > on left hand side menu set "Origin to Geometry".
If it still doesn't work, share the blender file with us or recreate the problem (if you can) in a separate project and share that file.