Learn English – a good word that means “group of groups?”

For parent-child relationships, ancestor works, or ancestor groups if you need to be explicit. An ancestor is a parent or parent of an ancestor. You could also use containing, inclusive, or maybe superordinate.

Inter means between. The Latin prefix for within is intra. However I wouldn't use "intra-ethnic" -- in fact I can't think of a sentence which would refer to "things within one ethnic group". One might talk perhaps of "inter-ethnic conflict", but "intra-ethnic conflict"? I think not: it would be "ethnic Europeans (for example) are fighting amongst themselves".