(Spoiler) Rupert's dog Fitzroy goes missing and then is revealed to have been 'consumed' by Despair in S3 but he is restored with everyone else after they defeat him.
For a brief moment in S1 EP7, Rupert believes that Porridge the Dragon died along with the forest and is upset, but right after it's revealed that he was just sleeping in a pile of daisies.
Not quite abusive, but Lavinia shows some toxic behaviors towards Rupert in the beginning (lying, gaslighting, ignoring his concerns, trying to force him into a marriage to distract him and the kingdom from the forest etc.)
Spoiler: both Rupert and Amir's fathers ( who were pretty bad people) are cursed to turn into trees. They are then destroyed and sink back into the earth, and kind of "die." In season 2, Wenceslas is a child and we dont know what happened to his parents.
The whole thing is pretty family-friendly. The only mildly sexual content is a one-off joke where Rupert says he can't wait for what comes after his wedding. If you count kissing as sexual content, then that happens too