No, no. Wrong person. Luca is obviously Jonas and Judith's sister's child.
The real question is whose childe is Jonas, because it's revealed that Jonas isn't actually a Winterwald, that's why Luca isn't.
The princess and the duke where never in that kind of relationship, she had Jonas with someone else. It was never revealed who that person was.
I remember reading a spoiler a long time ago saying the duke actually loved Sophia
It also mentioned how Joana’s mother got married with the Duke to free herself from her fathers grasp (it’s been a while I’m not sure)
Then there was something about how she used to leave at night and meet up with someone or some people and that’s when she got pregnant (again not sure but it was along these lines)
Would someone please spoil this for me: if Luca isn't part of winterwald, whose child is he? Or did the previous princess cheat on the Duke she married? Thank you.