Putting the father's last name on a birth certificate
My wife recently found her father, whom she had never met and about whom she knew next to nothing. Her father claims that he, in turn, never knew that her mother was pregnant and therefore never knew that he had a child. He was not married to my wife's mother. Nonetheless, his last name appears on my wife's birth certificate as her last name.
Assuming that what her father says about not knowing he was a father is true, how is it possible that his name would (or could) appear on the birth certificate as my wife's last name?
My wife was born in Florida.