Must A Secondary Category Be A Sub Category?

I have around eight or nine bottom level categories, each of which has sub categories. I am wondering if all secondary categories should be actual subsets of the Category. For example,

Dolls///Rag Dolls is a subcategory of my main menu category Dolls and Dolls///Play Dolls is another subcategory. A certain Raggedy Ann doll is both a Rag Doll and a Play Doll (some rag dolls are rare and therefore not play dolls). Is it OK and good practice to use Dolls///Rag as the category and Dolls///Play Dolls///Cloth as a secondary category? Thanks for any insights.

It's ok to do that.