It's not really incest, given that the creators have specifically said they're not related.
Source? AFAIK the only reason to think Ruby and Yang don't share genes, despite their dialogue, is that they have different last names. Everything else, from Monty's Twitter Q&A to the edits he (purportedly) made on tvtropes strongly suggests, if not outright confirms, that they are at least half-siblings.
Source? AFAIK the only reason to think Ruby and Yang don't share genes, despite their dialogue, is that they have different last names. Everything else, from Monty's Twitter Q&A to the edits he (purportedly) made on tvtropes strongly suggests, if not outright confirms, that they are at least half-siblings.