The question goes along the lines of understanding how does the entropy-information additivity works when black holes are inside other black holes, including the special case where the inner black holes have stable orbits around it.
Assuming one knows the separate entropy of two black holes $O$ and $I$, can one write down an expression for the entropy accessible on the outside spacetime when $I$ lives inside $O$? Is it an addition or a substraction of areas?
