The two of them are half siblings. Different fathers.
her dad definitely died when she was young
From what I understand she her dad was some other guy, he does amd then her mom somehow ended up with the emperor and had the little brother. They are half siblings.
Her dad was some fallen noble who died because he couldn't handle commoner work and wasn't able to adjust to the harsher lifestyle
wait wait if his dad is king how is her dad then she is older （￣へ￣）?