I've just finished a book by a history professor in the U.K. about the rise of Henry VII. (My question has nothing to do with the history, but use of language). Time is 1483. Henry is the son of Margaret Beaufort (and Edmond Tudor, deceased). Margaret is now married to Thomas Stanley. Lord Strange is the son of Thomas Stanley (by a previous marriage). In the book, Thomas Stanley is called Henry's father-in-law and Lord Strange is called Henry's brother-in-law. The terms I would use are stepfather and stepbrother. Is there an alternate usage in the U.K.?