Only Child Syndrome/Playing With

Basic Trope: A tendency for most characters in a work to be only children, save for when their siblings are important to the plot. Has various implications and effects on the setting in general.
 * Straight: Out of all of Sol's companions, the only ones with siblings are Ernst (with his Dead Little Sister Marie) and Princess Velvet (whose brother is the Evil Prince Satin).
 * Exaggerated: This lack of siblings extends to most of the world; there are very few uncles or aunts, resulting in even fewer cousins or other extended family situations.
 * Justified: They live in a Crapsack World where the population is closely monitored and most families can only have one child; only the higher class can break the law without facing severe punishments if caught.
 * Inverted: Nearly everyone comes from massive farm families with at least eight siblings who only receive mention as part of a Noodle Incident involving Alice being mistaken as a boy. Jacob is the sole exception. It's revealed that this is because his father fell apart after his mother died.
 * Subverted: Many of the characters' parents conceive after it is established that they only have one child each.
 * Double Subverted: However, their new children are immediately killed.
 * Parodied: ???
 * Deconstructed: The lower reproduction rate means that parents have one shot at passing on their genes; one tragic death at the wrong time can completely wipe out that branch of the family line. While a prophecy states that a descendant of a former Hero will become The Chosen One, the line is inadvertently snuffed out before the prophecy can come to pass. Hello, Endofthe World As We Know It.
 * Reconstructed: But prophecies can't be broken that easily, as a single member of the family line has secretly survived by pure chance. They just have to find him.
 * Zig Zagged: ???
 * Averted: All the characters in a work have varying numbers of siblings, from more than eight to none, few of whom are important to the plot.
 * Enforced: Law of Conservation of Detail keeps writers from creating siblings and family members that aren't important to the plot in some way, shape or fashion.
 * Lampshaded:"Hey guys, have you noticed barely anyone we know has any siblings?"
 * Invoked: ???
 * Defied: ???
 * Discussed: ???
 * Conversed: ???
 * Played For Laughs: A Running Gag is that whenever a character asks their parents why they're an only child, the parents always respond with some variation of "You're more than enough for us, sweetie." (The character never seems to pick up on the subtext that this meant they were too much of a terror for their folks to risk bringing another similar kid into their world.)
 * Played For Drama: According to prophecy, only the descendants of the last band of heroes can defeat the emerging evil once and for all. Unfortunately, there aren't too many descendants left, and the current generation is made up of only children -- which The Empire is hunting down one by one...
 * Ichigo is initially forbidden from accompanying Sol because she's her family's only child. Prophecy requiring her presence be damned; they're not going to lose their baby...!
 * Plotted A Good Waste: The lack of siblings turns out to be an important plot point, as it's an early sign that this world is not what it appears to be at first glance...

Back to Only Child Syndrome, and no, you don't have any siblings! There's only one Chosen One, after all.