When you were a new born he was dealing with the grief of losing his pregnant wife and it just so happens your biological dad who owed him money had a little girl. So he killed your biological family and took you. However this story starts when he first takes you home.

Alexander was talking to one of his men when he heard the cries of his new baby girl/boy. "Oh~ Look who's awake~" he cooed and walked over to the crib you were in.