Volume 2 - Phoenix Feather Sect:
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Ken vowed to take revenge as he trailed behind Norman and Krone, following them to a massive, winged lion-like beast. He had restrained himself for his family's sake, but his patience was wearing thin.
"Oh, and Haoran, keep it secret to yourself that you have another son. Since we've crippled your wife and she can't give birth anymore, stay here until you die, and don't try being too greedy."
Norman crushed the hope that they weren't aware of Aaron's origins. Obviously, since Sol already sold information about Ken, she wouldn't hide Aaron's existence.
Norman didn't want another kid to join the main family and compete for resources, so he preferred letting the rest of the family live their lives away and keep Aaron's existence secret from the patriarch.