I see you have a very strong resentment toward's a teen who's parents are not able to help her and grandparents who have die or soon will be dead.
Your dislike for this child living with you will be present immediately and will definitely cause her harm and your relationship. Its best to tell your bf, under no circumstances will you allow his neice to live in his home you share with him. It best he make other arrangements before she becomes homeless.
You do have the right not to share or to raise someone else's kid.
Hopefully no one will think of your child as someone else's kid.
Talk to him immediately.
