A container component similar to TRadioGroup?

Under Delphi 1.0, let's say I want to create a container component SIMILAR to TRadioGroup, but rather than translating the
contents of the TStrings property "Items" to a bunch of radio buttons, I instead want it to create a cluster of something else...  
for instance, a cluster of TButton's.  The goal: when one of the TButtons is clicked, it simply sets the "ItemIndex" value.

What's the best way to do this???

I'm experimenting with creating a new container component derived from TGroupBox.  The following identifies how I
approached this...

type TButtonGroup = class(TGroupBox)
     FBtnList : TStrings
     FItemIndex : integer;
     procedure CreateBtnsFromStrings(newList:TStrings);
     procedure ClearButtonList;
     constructor Create(AOwner: TComponent); override;
     destructor Destroy; override;
     property Items: TStrings read FButtonCaptionList write CreateBtnsFromStrings;
     property ItemIndex: integer read FItemIndex write FItemIndex;

I already have a routine (CreateBtnsFromStrings) which creates the buttons.   My problem lies in HOW the strings are passed to
this routine, via the Items property in the "published" section.  When I click the ellipsis button ("...") in the object browser, Delphi
responds with the message "Cannot assign a nil to a TMemoStrings".

So what is this beginner doing wrong?

Thanks for reading this, and for your help.