When it comes to the term "crown princes," there are a few synonyms that can be used to describe individuals in this prestigious position. One such synonym might be "heirs apparent," as these are the individuals who are next in line for the throne. Another option might be "prince regent," which refers to a prince who is ruling in the stead of an absent or incapacitated monarch. "Successor princes" could also be a helpful phrase to use, as it communicates the idea of an individual who is next in line to inherit the throne. Ultimately, all of these synonyms can be helpful when discussing the topic of royalty and succession.