Raben (plural of Rabe) are ravens and Eltern parents. In combination, they refer to parents who neglect, if not abuse, their children. If you want to refer to a bad mother or bad father individually, you can use Rabenmutter or Rabenvater, respectively.
These words are common in German, although they do give ravens an undeservedly bad rap. When one finds little ravens outside their nest before they are able to fly, it's not, as people thought, because their parents wanted to get rid of them, but because they are safer there from predatory birds like hawks. [Sick 2012]