Part of it is having various athletes receiving blindfolded special kisses from a secret admirer.
Sexuality, incest and repeated reference to his paternal grandmother as a witch - are some of the subjects Partha De has written about sporadically in his diaries.
Great job telling your story! Also there's a bit of a twist, what with them being royalty in Egypt, where royalty traditionally marry relatives, so the Morpork-educated brother is probably the only person in the kingdom who has a problem with it.
Let's not forget that both Kurei and Kurenai were in love each each other and actually a couple in canon.
Granted, no tongues were used that we could tell, but it still ignited speculation that there was something more than simple sibling love going on between the two.
According to her ghost, at least.