As Ayame's brother, Weiss wasn't oblivious to Ayame's popularity. She was popular to the point that as long as someone didn't live under a rock and would often use the internet, it was impossible for them to not know of Ayame.
Compared to Ayame who was very famous, Weiss wasn't as popular as she was. After all, he only served as Ayame's hacker and only those fans of hers who were keen on checking every information about Ayame would know of his existence.
Even in the hacking world, Weiss rarely made any appearances as he didn't even need to commit cyber crimes for the sake of money since he had a lot of it. He was only present if ever a hacker dared to provoke Ayame and tried to threaten her.
As Ayame's brother, Weiss didn't have to worry about Ayame since she was very independent. Even now, Weiss still relied on Ayame's popularity and fan base to promote his game.
