im not sure.... though from the looks of it, it is male heir succession. but because avery is her father's only child, she would be the one to succeed the ducal position.
I believe that whoever marries Avery would be the next Duke, same way that her aunt's husband became an earl when he married into the family after she killed off her first brother (her husband wasn't able to become the dude's successor since Avery (father) was still alive and could've had a boy). Plus I doubt the duke would want the daughter who killed his two sons to become the duchess...
I think it follows loose patriarchy rules. Inheritance goes to the eldest son, and if there is no son, eldest daughter. Since Avery's father had no other children, she would be his heir, and since he died, she takes his place in the line of succession from the Duke. The same thing happened with Queen Victoria. Her father was in line for the throne, but he died, so she took his place in the line of succession. Then a lot of stuff happened and she became queen.
Wait!!! I'm confused.
This comic follows which type of succession? Patriarchy/male heir all the way or the 1st born
child regardless gender is the successors?