Daniel's brother Sean, 81, maintains that he didn't actually contribute to the book though, except to give the author a copy of the biography he penned on their famous poet father, Cecil Day-Lewis.
"I wanted to get the facts right, and he didn't even do that," Sean said, according to the National Enquirer. "He got birthdays on the wrong days. It was full of errors. Anyway, he acknowledged my help in the foreword, and Dan saw that and completely blew me out of the water."
According to the Enquirer, Sean has been desperate to get back in touch with Daniel, 55, but the furthest he got was a phone call in 1994 when the Lincoln star told him to "f**king get a life" and to "f**k off."
To find out the full story, pick up the latest issue of the National Enquirer -- on newsstands Thursday.