some one is useing our father last name it's leigal , claims to be sister to us. what leigal action can we take.
If a person is using their legal name that is on their birth certificate then there is nothing you can do about it.
If this person has legally changed their name by a judge to this name, then there is nothing you can do about it.
If you have a question about this person using your father's last name, I suggest that you consult with an attorney in person.
I hope this information has been helpful. Without more information I cannot address your question more fully. Sorry.