After their mother has died, two young siblings, a boy and a girl, are mistreated by their Wicked Stepmother, so much that they decide to run away from home. But the stepmother, who is also a witch, enchants the streams of the forest where the children are wandering, so that drinking from them would turn them into animals. The girl sees through the trap and talks her brother out of drinking from two streams that would have turned him into a tiger and a wolf, but when they come upon a stream that turns people into deer, he is so thirsty that he doesn't care any more, and turns into a roe fawn.
Later, the two find a deserted cottage in the woods and decide to live there, fending for themselves in the wilderness. Years have passed when a king and his court come to the forest for hunting, and the brother makes a game of making the hunters chase him, then hides in the cottage in the evening. But the second time he tries this, he is wounded, and thus leads the hunters to the cottage.
On seeing the sister, the king falls in love with her and asks her to marry him. She agrees to come to his castle, but only if the deer, her brother, can come too. Thus she is made queen, and the brother lives in the royal gardens. After a while, the sister has a child with the king. But by now, the evil stepmother has learned that the siblings are still alive, and, driven by hate and envy, plots to destroy their happiness...
"Brother and Sister" contains examples of the following tropes:
- After-Action Patch-Up: After the second hunt.
- Animorphism: The brother is turned into a deer.
- Back from the Dead: After being suffocated in a bathhouse by the sorcerous stepmother, the sister returns as a ghost to look after her baby. But when the king recognizes the spirit as his true wife, she is miraculously restored to life by God.
- Baleful Polymorph: The cursed stream turns the brother into a deer.
- Beauty = Goodness: The sister is described as the most beautiful woman her husband had ever seen (and since he's a king, that's saying something), and is portrayed as kind and loving. The stepsister, on the other hand, is utterly repugnant in both appearance and personality.
- Big Bad: The heroes' Wicked Stepmother, who has made it her mission to ruin her kids' lives.
- BrotherSister Team: Well, sort of...
- Burn the Witch!: How the stepmother meets her end.
- Changeling Tale: The stepmother-witch kills the sister and (apparently hiding the body) replaces her with her own ugly daughter, which she magically made look like the sister.
- Disappeared Dad: The father of the siblings has not a single appearance in the whole tale. All we know about him is that he must exist.
- Double In-Law Marriage: In some versions, the king has a sister who the brother marries after becoming human again.
- Evil Cripple: The one-eyed stepsister.
- Food Chains: The brother's transformation is caused by drinking enchanted water.
- Gray Rain of Depression: "Heaven and our hearts are weeping together."
- Love at First Sight: "Will you marry me?" are literally the first words the king speaks to the sister, having met her about half a second before. And the sister doesn't take long to decide that yes, she is willing to marry a total stranger.
- The Marvelous Deer: A Justified Trope: The Brother, transformed into a roebuck wearing a golden collar, makes a game of making the king and his hunters chase him, then hides in the siblings' hidden cottage for the night. Eventually, the pursuit of the mysterious roebuck leads the king to the hovel, where he meets a beautiful woman (the Sister) whom he falls instantly in love with.
- Nameless Narrative: Everyone is referred to by their relationship to each other: the brother, the sister, the king, the stepmother and the stepmother's daughter.
- No Ontological Inertia: When the stepmother-witch is executed, the curse of transformation on the brother is finally broken, and he turns back into a man.
- Rags to Royalty: The poor siblings end up as the wife and brother-in-law of a king.
- Red Right Hand: The witch can make her daughter look like the sister with her magic, but she cannot hide her missing eye.
- Rule of Three: It's from the third spring they encounter that the brother drinks from, and thus is turned into a deer. It's also during the third day the king and his court are out hunting that the king encounters the sister.
- Talking Animal: After his transformation, the brother is a talking deer.
- Trap Is the Only Option: The brother is so thirsty that he finally drinks from an enchanted well even though he knows it is cursed.
- What Happened to the Mouse?: It is never explained what the Hell the witch did to the Sister's body after killing her. Some adaptions handwave it by having her magically turn the Sister into a ghost rather than actually killing her.
- Philip Pullman's Grimm Tales version has the stepmother hide the body by sealing the room with magic and hiding it behind a tapestry.
- Grimm's Fairy Tale Classics solves this with Bowdlerization: The Sister is kidnapped and not killed, but she's greatly weakened whenever her spirit projects itself in the castle to breastfeed the baby prince and she will soon die from such an effort. Fortunately, her husband the King finds her before she exerts herself to death.
- Wicked Stepmother: Cinderella's stepmother is an amateur compared to this one.
- Wicked Witch: The stepmother is also a proficient sorceress.