Jonas (Luca's dad) is not the dukes son.
Judith is the granddaughter of the sister of the former king (her grandmother elope with a commoner)
Lucas is the one that make a wish to the family gobling (only a royal heir can do that) to reverse time. So he has his past memories.
Judith has always been Judith. Explanation, so when she died as Judith she reincarnated in Korea (no memories of her life as Judith) when Lucas reversed time she died in Korea and went back in time before she died as Judith.
Lucas will ask to get removed from the family tree, as he is not a heir in the family.
Duke always knew that Jonas wasn't his son. He and Vanessa had made a deal. Vanessa wanted freedom from her father and he wanted a royal baby (because they are protecting the wish gobling to don't fall in the wrong hands but only a royal blood can use the wish)
The Duke killed Jonas because Jonas wanted to become a king using the wish and that is treason. But what made the Duke to kill him was that Jonas wanted to kill Sophia and Duke has done everything because he loved Sophia.
Duke doesn't really care who will be the heir from the moment they will protect the wish gobling and will let him and Sophia alone.. Duke accept Vanessa's proposal only because Sophia was her lady in honor.
Judith as a descent of the royal family can make Rudy an heir. (As you need to get married to a royal family to become the Duke or being from a royal blood)
She and Rudy will get married and will have a daughter.
There are some side stories I haven't read them all.
Does anyone would like to spoil me? (▰˘◡˘▰)