According to the book of record, although the Grimsbanne Clan never took part in royal affairs and politics, they were still a part of the nobility. It was just that they steered clear of anything and stayed inconspicuous. Although they were infamous for many things, such as having the purest form of blood and being descendants of the devil, being a nobility wasn't a part of it. Therefore, that fact was buried until it was nearly forgotten.
Aries read about it before, making use of her free access to the royal library where a good deal of information about the royalties, nobilities, and the mainland was recorded. She didn't give much thought to it before because she didn't find any reason to dwell on it.