Okay I have a theory. Okay maybe not one but several theories.
What if uriel is actually not her real brother but her nephew (the son of the current Duke Orphe's brother and that maid) but in previous timelines he was not brought into the family and it gave a valid reason for the Baron to be able to use him to fight against the dukedom and it also cause for Uriel in the previous timelines to grow to hate the Orphes (perhaps due to the Baron's teaching) and he along with the baron waged attacks after attacks until Lamia's eventual death.
In this timeline however Prince Aquila had manage to somehow make the dukedom bring him into the family and the dukedom decided to keep Uriel's real identity a secret even from Lamia and Uriel himself. However, Aquila couldn't quite forget the things Uriel did in the previous timelines and chose to attack his hand. And what he means by the things he said about attacking his family is actually a reference to his real family (the maid and the baron protecting him in the previous timelines) and not his current family because Aquila had been aware of what they did in the previous timelines - hurting Lamia. So Aquila did the attack out of momentary vengeance and also to ensure that Uriel will be the next heir to the dukedom and cause for the Baron's current attacks on the dukedom to be invalid right after it is announce that Uriel is the heir to the dukedom instead of Lamia. So it prevents future attacks from happening too because it's now certain that Uriel would inherit the dukedom instead of Lamia. So in the end it ensures Lamia's safety.
But one thing that Aquila had missed out is that Uriel has now become a valuable member of the family and to Lamia so hurting Uriel is like a direct insult to Lamia too. And another thing that he also missed out is that Uriel in this timeline did not turn out bad because he grew up in the dukedom and is no longer influenced by the Baron. So it couldn't have been possible that he in this timeline would harbour malicious intentions towards the dukedom or Lamia. So when Uriel hears the threat against his family he immediately assumes that Aquila is threatening the dukedom which is his family now and not the maid and the baron who protected him at one point in this timeline and in the previous timelines.
Yes Aquila has a valid reason to be mad at Uriel's real family and possibly Uriel too because they might have killed Lamia and her father in previous timelines but what he missed out is that Uriel is no longer part of the bad guys cause he grew up within the dukedom.
And I feel like the thing that solidifies this theory are the events that happened in prologue chapter 3. In that timeline it seems like there's no sign of Uriel at all cause
1. Lamia is wearing a dress which means she DID become the heir to the dukedom and didnt become a knight
2. For a sister who's so devoted to caring for her brother, why does she not even mention him to Aquila once?
3. The location they're in seemed to be in Lamia's homeland cause of her mention of the region's specialties. If she were to become a knight she should be at the capital instead of her homeland which goes to show that she DID became the heir
4.There's no sign of Uriel at Lamia's funeral.
And the reason to all those is because in the previous timeline Uriel DIDNT enter the dukedom and become her brother but was fully raised by the Baron instead.
Other small details that I noticed now from the prologues is that this is not the first time for Aquila to turn back time. And I'm guessing that the events in the current chapters is the 4th timeline. Meaning it's the fourth time he turned back time. And in this timeline he chose to save Lamia's father to prevent the disasters that might happen to Lamia in the third timeline. And he also hurt Uriel to prevent him from being a knight and instead be the heir to the dukedom to prevent the attacks from the Duke.
The events in chapter 2 might be the third time he turned back time, and in that timeline he brought Uriel to the family, possibly hurt Uriel too to make him the heir which is why we see Lamia deciding to become a knight. But in this timeline he didn't save the Duke and I assume something bad still happened to Lamia which cause him to start the current timeline.
The first scene in chapter 3 is possibly from the second time he turned back time in which in this timeline he and Lamia were able to grow close and are able to fall in love like in the original timeline but he didnt bring in Uriel to the dukedom in this timeline which cause for Lamia to die because of the attacks from the baron.
Meanwhile the scene where Lamia reached out to him is the original timeline in which he and Lamia truly fell in love with each other to the point that they got engaged (look at the two rings he was holding before he made a promise to make spring come to Lamia again). In this timeline, Uriel is also not her brother and Aquila and Lamia possibly fell in love like any romance leads does but Lamia got killed in the end maybe from the baron or maybe from an unknown enemy. But the events in this timeline is what prompted Aquila to start the 2nd timeline but failed to save Lamia again then he start the 3rd and failed again and now he started the 4th timeline.
Because he turned back not once but 4 times he knows more about what will happen and that he shouldn't apologize to Uriel just yet, possibly to prevent the events in the third timeline from happening.
So yeah that's my crazy long ass theories. Thank you for coming to my Ted talk today and I look forward to read the real explanation to the comic
