Random thought, more than one of the princes are Beyond's child. Considering how long he's been preparing, it seems likely that he wouldn't take a gamble on how long before his father dies and having a prince (his child) be young enough to be easily controlled.
The most likely ones I think are the princes with dark hair. Sevanti says that Marayam's protection is more important than Momoze, and Seiko's thoughts on Kacho dying so soon means Fugetsu loses a shield hints they have deeper reason for their favouritism. Tyson and Luzurus haven't had much screen time, and Zhang Lei is probably too old for Beyond to have much interest in him winning, though his lack of knowledge of nen, despite being one of the older princes does seem odd.
Can't be bothered to think more deeply about this for now. zzzzz