re: vimes' father
IMO, in NW, there's a hint that sams father didn't exactly die, i think the quote says something along the lines that vimes asks young sam about his father, and sam says that his mother told him that his father was run over, and vimes thinks "that's what she wants you to think. what a champion liar his mother had been, too."
another thought, a quite critical one, at that. while i absolutely love vimes and he is my favourite character in all the books, one thing that always bothered me was the scene in the unmentionables' watchhouse where they find the people in the cells and vimes "...drew his dagger and without remorse gave...what help he could." how does one justify that?