Sister

I think that's his sister. She told him about his mother and sister loving him, right?

Didnt his dad ask his assistant (dude with dark hair and glasses) if his father killed his daughter and he said he took the baby to the forest and left her? I think Alexandro had an infant sister that was left for dead which might also explain why the mom really hated Duncan (Alex’s dad) if his quest to be emperor came with so much danger including the death of their infant daughter by an enemy ? So his mom didn’t hate him but resented the dad and the sister he never met because she died loves him as well