File list (Check if you may need any files):
VariablePassing\ParentToChildCS
...............\...............\App.ico
...............\...............\AssemblyInfo.cs
...............\...............\ChildForm.cs
...............\...............\ChildForm.resx
...............\...............\ParentForm.cs
...............\...............\ParentForm.resx
...............\...............\ParentToChildCS.csproj
...............\...............\ParentToChildCS.csproj.user
...............\ParentToChildVB
...............\...............\AssemblyInfo.vb
...............\...............\ChildForm.resx
...............\...............\ChildForm.vb
...............\...............\ParentForm.resx
...............\...............\ParentForm.vb
...............\...............\ParentToChildVB.vbproj
...............\...............\ParentToChildVB.vbproj.user
...............\SiblingToSiblingCS
...............\..................\App.ico
...............\..................\AssemblyInfo.cs
...............\..................\ChildAForm.cs
...............\..................\ChildAForm.resx
...............\..................\ChildBForm.cs
...............\..................\ChildBForm.resx
...............\..................\ParentForm.cs
...............\..................\ParentForm.resx
...............\..................\SiblingToSiblingCS.csproj
...............\..................\SiblingToSiblingCS.csproj.user
...............\..................\ValueUpdatedEventArgs.cs
...............\SiblingToSiblingVB
...............\..................\AssemblyInfo.vb
...............\..................\ChildAForm.resx
...............\..................\ChildAForm.vb
...............\..................\ChildBForm.resx
...............\..................\ChildBForm.vb
...............\..................\ParentForm.resx
...............\..................\ParentForm.vb
...............\..................\SiblingToSiblingVB.vbproj
...............\..................\SiblingToSiblingVB.vbproj.user
...............\..................\ValueUpdatedEventArgs.vb
...............\VariablePassing.sln