Basic Trope: The youngest sibling is The Hero or the best in life success/luck in general.
There are three brothers: Ace, Bob and Chris. The elder brothers look down on Chris, thinking him a fool, yet when it comes time to venture out and prove themselves, both Ace and Bob fail miserably, while Chris saves a kingdom and earns the Standard Hero Reward.
There are three sisters: Alice, Eva and Iris. Iris is the most beautiful, compassionate, and talented of the three; while her sisters are also pretty, they're vain and haughty, and are thusly ignored when Prince Charming comes calling.
Exaggerated: Lance is the youngest of twelve brothers, and the only one who achieves anything of importance with his life, going from a simple Farm Boy to ruler of half the world.
Justified: As the youngest, Chris won't inherit much of their family's fortune, and so has more invested in finding his own riches.
Inverted: Ace is The Hero that sets out and does everything, with Bob helping out, while Chris is lazy and spoiled.
Chris is nothing special compared to his older brothers.
Iris isn't particularly pretty compared to her older sisters.
...Or, at least, people think Chris is less talented, but he turns out to be smarter and better skilled than they realized.
Iris isn't as pretty as her sisters at first, but has a beautiful heart, and when she gets older...
Or, Chris is very spoiled and lazy, but is Genre Savvy enough to realize that he's in a fairy tale, thus making him immune to bad endings. While Ace and Bob work their hardest to achieve their goals (without any success, since they're the older brothers), Chris just sit on his bottom getting daily rewards from the magical fairy (which would later be his wife, and also happens to be a transformed horrendously ugly dog he took care of, knowing that it will somehow help him).
Zig Zagged: ???
Averted: Chris, Ace and Bob decides to work together and share the reward fairly, and even after decades, none of them is better than the other.
Enforced: The work is providing Wish Fulfillment for its target demographic of young kids; "Yeah, your brothers might make fun of you and beat you up now, but you'll end up on top eventually."
Lampshaded: "Why am I not surprised the youngest of us gets to be The Chosen One?"
After proving himself better, Chris arrogantly pays them back for all the years they spent tormenting him as their 'foolish, worthless baby brother'. Ace and Bob struggle with how he's completely overshadowed him, and their resentment breaks the family apart.
Alice and Eva are so frustrated with everyone praising their sister's beauty that they disfigure her.
Chris is Wrong Genre Savvy — this isn't a "youngest kid is the cunning one" story, this is an "overlooked middle child proves himself the well-adjusted happy medium between both his brothers" story, and Bob is the hero.
Reconstructed: After Chris finally outshines his brothers, they fall out of communication, but Bob and Ace finally talk to their younger brother after realizing they need his help, and Chris finds he is no better than his bothers if he ignores them.