Public Class aaMyForm
    Inherits Windows.Forms.Form

Added some controls. Build it, add the .DLL as reference to my other project.
In my other project:

Imports MyLib
Public Class XForm
    Inherits aaMyForm

The events from aaMyForm execute correctly but the controls added to it are not shown on XForm. I have found some info about set Modifiers Protected in order to be able to change the functionality of the controls but havent found anything about why the controls aren display on the XForm.

I think I found the problem. I was creating a new class that inherited from Form instead of creating a new form, which I thought was pretty much the same (both are classes that inherit from form) but the new form, has the .designer.vb file where the InitializeComponent resides, while when creating a new class that inherits form Form doesn't and so the InitializeComponent is not on the Partial part of the class.

So the solution is creating MyForm class directly by adding a new form instead of creating a class that inherits from Form. Now if a form in a different project inherits from MyForm it does contain the controls. I would still like to know the exact reason for that. Thank you all.