Basic Trope: A relationship between siblings is complicated by the introduction of another sibling.
- Straight: Alice and Bob are a Brother–Sister Team or having a Sibling Rivalry. When Carla, an Annoying Younger Sibling, is introduced, things get awkward.
- Exaggerated:
- Alan and Bob are already bitter enemy siblings that hate each other, but when the Annoying Younger Sibling Carla has arrived, things go downhill from there.
- At least one additional sibling (either a Big Brother Bully or an Annoying Younger Sibling) is introduced to each family in the work, causing a complete and total Big, Screwed-Up Family each.
- Alice and Bob are revealed to have 120 previously unseen siblings, who are treated as if they had always been around. Some or all of these new siblings reappear later on, greatly complicating Alice and Bob's Big, Screwed-Up Family situation.
- Downplayed:
- Carla slightly complicates matters.
- Alice and Bob are minor characters anyway.
- Justified:
- Annoying Younger Sibling Carla only moved into town recently.
- Carla is a baby.
- Inverted:
- Bob dies, altering Alice's personality.
- Same as above, except Bob is erased from existence via time travel.
- Subverted:
- Carla has no effect on Alice and Bob's Sibling Team dynamic.
- Alan and Bob plan to murder each other, but their sister Carla arrives here to stop it.
- Double Subverted:
- However, when David and Emily's brother Frank is revealed, the plot falls into chaos.
- But ending up seeing Bob murdering Alan in a standoff and berating Carla for being an Annoying Younger Sibling, Carla kills Bob in a Roaring Rampage of Revenge.
- Parodied:
- Flashbacks are a recurring element in the show, and at first, they only show Alice, Bob, and their parents. After Carla is introduced, she starts appearing in the flashbacks.
- Alan and Bob steals each other's toys, but Carla arrives and steal them all, makIng them berating her for being an Annoying Younger Sibling.
- Zig Zagged: ???
- Averted: No new siblings are introduced.
- Enforced: ???
- Lampshaded: "I didn't know about Carla." "Neither did we. I guess we kind of forgot about her after we went our separate ways."
- Invoked: Carla moves to Troperville, knowing that her siblings already live there.
- Exploited: ???
- Defied: Carla avoids her siblings.
- Discussed:
- "No, we don't have any other siblings. It's just Alice and I. And it's a good thing, too, because she's the only relative I need."
- "Alan, we do have grudge against each other, but hey, our sister Carla hates us!"
- Conversed: "So, they had another sibling all along? I never would have guessed."
- Implied: Carla is not explicitly stated to be Alice and Bob's sister, but she strongly resembles Alice.
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