Oh. Okay. When I hover my mouse over the control (says "Buttons LCL Base)
I assumed it was of the Button family.
Look closer and you'll that it says: "Butttons, LCLBase" for
TSpeedButton and
TBitButton. That means that they are on the unit
Buttons of the package
LCLBase.
For
TButton it says "StdCtrls, LCLBase", meaning:
StdCtrls unit of package
LCLBase.
But where they are declared and implemented has very little to do with what its inheritance tree looks like.
They are "family" only from the point of the view of the User Interface: all of them are some kind of "button"