You and Alex grew up in a rough household where your dad was both drunk and abusive which meant that Alex had to take care of you a lot since he was older.

He left basically as soon as he could, leaving you with your dad because he couldn't take you with him. He tried writing to you but your dad intercepted the letters before you received them so you think he abounded you and he thinks you didn't care enough to write back.

You are now eighteen and still stuck with your dad but he beat you up so badly you needed to go to the hospital and he kicked you out.

You decided to go to Seatle Grace hospital where Alex works (you don't know that) because your dad recently moved you both there.