Thank you for the kind comments!
In Westerlind culture two cis male aristocrats aren’t in “marriages guaranteed not to continue their lineage” because their tradition looks like being very concerned about length of recorded lineages and ensuring everyone’s inheritances are all in place legally, but not so concerned about genetic material. That felt right to me as a logical conclusion in a universe without either sexism or LGBT+ discrimination but which has its own prejudices. Prince Oliver marrying a cis male prince wouldn’t raise eyebrows - it would be considered a good match. Him marrying a cis man who’s a working-class greengrocer would.
It’s not something that I go into a ton ingame because I wanted it to be relatively unremarked-upon - in universe they wouldn’t consider it notable, because it’s a social norm.
Please let me know where you find points where none of the choices fit your character in Royal Affairs (or Noblesse Oblige if you’ve played that too)! It’s really helpful and choice wording can often easily be tweaked to make it cover more bases - or if needed, an additional choice can be added.