That would mean that these shapes get a common parent once rotated. And if you change the selection to include some but not all, and maybe some other shapes, an

That would mean that these shapes get a common parent once rotated. And if you change the selection to include some but not all, and maybe some other shapes, and rotate, you'd create a many to many relationship? Maybe the appropriate choice here is grouping, like we see app use folders for these. That way you get what you're talking about and it's obvious to the user / it's based on their choice.