Terry Pratchett's Wyrd Sisters (1997)

Based on the Terry Pratchett novel. On Discworld, in a small country called Lancre, three witches, the flowery Magrat Garlick, the lively Nanny Ogg and their leader Granny Weatherwax find themselves dragged into royal politics. The king of Lancre, Verence, has been murdered by Duke Felmet and he has taken over control of the country (but he is trapped under the control of his over-powering wife - the Duchess.) The Duke hates Lancre and the actual kingdom of Lancre is pressing the witches to find a king that would take better care of it. The second and bigger problem is that Verence's baby son has escaped and has fallen into the hands of the witches prompting the Duke's fury towards the witches. The son must be protected but Granny doesn't want to get involved with the situation but it looks like she doesn't have a choice in the matter...