[Lazarus] constructor Create How is it work?

[FreeMan]

Hello,
constructor Create how is work ? In IDE not problem, but In application, 
form created AOwner not nil, self created, FGrid created, but 
Self.Parent is NILL ??? Self.left is 0 (not because its 10) all 
Self.BoundsRect value is 0. Why? for test I added that code to in 
@EditChange procedure (FGrid.Parent  := Self.Parent; this line and 
later)  values is been correct, But in create not work properly.
Has any one any idea?
Thank you

type
   TExLookUp = class(TCustomEditButton)
   private
     FGrid: TRxDBGrid;
   Public
     constructor Create(AOwner: TComponent); override;
.....
constructor TExLookUp.Create(AOwner: TComponent);
begin
   inherited Create(AOwner);
   Self.OnChange  := @EditChange;
   FGrid := TRxDBGrid.Create(Self);
   FGrid.Parent  := Self.Parent;
   FGrid.Left  := Self.Left;
   FGrid.Top   := Self.BoundsRect.Bottom-4;
   FGrid.Width := Self.BoundsRect.Right - Self.BoundsRect.Left;