I Don't Love You Anymore - Chapter 23

Um, pretty sure it is implied that Rudi is the son of Joachim’s brother and the Thierry princess. The whole “you’re the reason why I’m looking in Thierry” and then Thirrry commenting on the prince knocking up the foreign princess and Joachim shrugging it off they’re in love. Meaning Rudi is like a cousin to the crown prince but not probably on good terms