In Visual Studio, two files are created when you create a new Windows Form in your solution (e.g. if you create MyForm.cs, MyForm.Designer.cs and MyForm.resx are also create
Yes, but it's a bit of a hassle - basically you need to edit the project file by hand.
Here's an example from a project that Marc Gravell and I both work on:
DataProducerExt.cs
DataProducerExt.cs
DataProducerExt.cs
DataProducerExt.cs
DataProducerExt.cs
Note the "DependentUpon" element in each of the dependencies. This displays appropriately in VS, with DataProducerExt.cs as the parent.