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.
Enforced: "We need to provide Wish Fulfillment for our target demographic of young kids." "Let's have Chris, the baby of the family, get rich, while his Big Brother Bullies Ace and Bob end up homeless."
Lampshaded: "Why am I not surprised the youngest of us gets to be The Chosen One?"
Chris deliberately screws up Alice and Bob's attempts to earn a living.
Exploited: Ace and Bob are lazy and mooch off of Chris.
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.
Chris shares his wealth with his brothers.
Discussed: "I wonder who will come out of top?" "Probably Chris, because the Youngest Child Wins every time."
Conversed: "Why does the youngest child always win out? It's terribly unfair. Some of us viewers are older siblings, you know."
Implied: Chris lives in a nicer house than Ace or Bob.
After Chris finally outshines his brothers, they fall out of communication.
Alice and Eva are so frustrated with everyone praising their sister's beauty that they disfigure her.
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 brothers if he ignores them.
Played For Laughs: While Ace and Bob work their hardest to achieve their goals (and fail because they're older than Chris), Chris gets daily rewards from the magical fairy who will later be his wife. Said fairy also happens to be a transformed horrendously ugly dog he took care of years ago, knowing that it would somehow help him.
Played For Drama: 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.