Normally, the naming Rel<ParentClass><ChildClass> works well, but as you mention, when you have a relation between the same class it doesn't work very well. We have the same case internally a few places:
- for the Parent/Children relation used for the tree structure. We don't use the class at all, and called it RelHierarchical.
- for the ProductCategory class and the ParentCategory and Subcategories properties, we have called the relation RelProductCategorySubCategory.
Many e-commerce sites have a RelatedProducts relation. It is a relation between products. We often call this relation RelProductsRelatedProducts (m:m).
Hopefully some of the examples can give you some ideas for consistent naming of the relations that works well for your use-case.