That name was not unknown to anyone in this world. A person who is a Primordial Heir receives such an amazing inheritance that in every corner of the universe they are known.
Even the lower worlds know about them; how could this pair of brothers not? Although it may not seem like it, they both have a good background in their world. Being a Level 5 Civilization, they have a lot of information.
That kind of Heirs occupies a unique place in the universe in terms of status. Status cannot be achieved by mere whim or effort; you need to go through an unknown process of choice or simply be born with an absurd affinity towards a Primordial Law.
Besides, it is not easy to see such people. Although they exist in the universe and have great status, if you see one of them, you might already consider that you had the luck of your whole life or the misfortune of your ancestors. This is because they usually live in the Primordial World, something that many people believe does not exist.