"So we have Blossom, Bubbles, and, hmmm, Buttercup because... it also begins with a B."—Professor Utonium, The Powerpuff Girls
A form of Theme Naming in which everyone in a family, or one generation of a family at the very least, all possess names with Alliteration, starting with the same letter or syllable. Bonus points if their last name also starts with the same letter. While obviously this can be expected to be intentional on the part of the writers, it can also be shown to be deliberate on the the part of the characters. Such characters will usually be a little on the quirky side, if so.
May or may not also be an Alliterative Name, in which both first and last names have the same letter. The Theme Naming can be taken even further when these same letter names all have a theme within the same letter. When done In-Universe by the characters, can overlap with Who Names Their Kid "Dude"? and can lead to Rapid Fire Name Guessing.
Sub-trope of Theme Initials, in which several characters who may or may not be related share the same initials, and of Family Theme Naming, in which members of one family have related names which may or may not be alliterative.
- Superman's Girlfriend Lois Lane and her sister Lucy. Mother's name is Elinore, so it almost counts too.
- The Sandman features the Endless, seven siblings who are named for what they are Anthropomorphic Personifications of, Destiny, Death, Dream, Destruction, Despair, Desire and Delirium (originally Delight).
- Though it's never explicitly stated, "Groo" appears to be a family name of sorts—Groo's sister is named "Grooella", and his grandmother is Granny Groo.
- Harry Potter's Albus Dumbledore had two siblings, Aberforth and Ariana.
- Voldemort's family (the Gaunts) also counts: Marvolo, Merope, & Morfin.
- In JRR Tolkien's Middle-earth (The Lord of the Rings, etc) it is extremely common for families to have names with similar meaning or sound, and as such there are many with alliterative names.
- It happens in two of the three major human families in The Silmarillion. Twenty-three members of the house of Bëor (out of about thirty) have names starting with a B. There are slightly fewer Haladin, so there are slightly fewer characters whose names start with an H...but six of them have names starting with "Hal".
- A hobbit example would be the siblings Peregrin (Pippin), Pearl, Pimpernel, and Pervinca, children of Paladin Took.
- The names of all seven Lightbringers (gods who claimed to be siblings) in Arcia Chronicles started with an "A".
- The Nita family in Breaking the Wall all have names starting with "N." One character, two year old Lani, seems like an exception until you realize her name is short for Nolani.
- An episode of Mr. Belvedere, "Moonlighting", featured the Bilinski family, Burt, Buzz, Brenda, and Bobbi. When introduced to the Owens family, Buzz mocked them because their names all started with different letters.
- The Halliwell sisters in Charmed all have names starting with the letter "P". As do their mother and grandmother.
- Rhymes, not alliteration: On The Bob Newhart Show Howard Borden had two (unseen) brothers: Gordon Borden the game warden and Norman Borden the Mormon doorman.
- To go with the rhymes, not alliteration- on Newhart, there was a Larry, who always came in and introduced his brother Daryll, and his other brother Daryll.
- Glee: Sam Evans's parents are unseen, but his younger siblings are named Stacey and Stevie.
- Rowan and Martin's Laugh-In had the Farkel family: Frank & his wife Fanny, and their kids (some alliterated, some rhymed, and some were just puns) - Sparkle (& her sometimes twin Charcoal) Farkel, twins Simon & Gar Farkel, Mark Farkel, Fritz, Flicker, and Fred Farkel. None of the kids looked like Frank but they all looked like his "friend and trusty neighbor" Ferd Berffle.
- A '70s Sesame Street News skit had Kermit the Frog reporting from Piper's Pickled Pepper Patch, hoping to get an interview with the famous Peter Piper. After running into relatives Porter Piper, Potter Piper, Piper Piper, Papa Piper, and Parker Piper, he finally learns that Peter's "in Portland, pressing pants."
- The present generation of the Hyuga Clan's Main Branch in Naruto all have names starting with H-sounds. Hiashi, Hinata, and Hanabi. Hiashi's brother was named Hizashi.
- Kamichama Karin has this happening in two families, Karasuma and Kujyou, which both use K-sounds. We have Kirio and Kirika on the former side and Kazuto, Kazune and Kazusa (and, by marriage, Karin) on the latter. Both families also have a Himeka.
- The Azukis of Bakuman｡, with Miyuki and her daughters Miho and Mina. Her husband is unnamed.
- Bill Cosby gave all five of his kids names beginning with E, supposedly for "excellence".
- Vince Vaughn's father is named Vernon and his sisters are Victoria and Valeri. He's mentioned in interviews that the alliteration continued in pets names as well (such as Vlade and Valiant).
- Taken to ridiculous extremes by retired boxer George Foreman, whose sons are named George, George, George, George, and George. And two of his daughters named Freeda George and Georgetta.
- Ambrose Bierce is another real life example. His father gave all the children names starting with "A".
- While it extends over more than just alliterative names, it is very, very common for siblings in Denmark to have similar names, especially if they're the same gender. It goes from slight resemblances like Anton and Arthur to almost identical names like Christian and Christina. Guess we aren't too creative around here...
- For Chinese Names (as well as in several other cultures influenced by old Chinese naming conventions), it is a tradition in many families for brothers to have the same Chinese character in the same position ("generation name", That Other Wiki calls it). In some families, there are even more rules on top of this such as consecutive generations using the next character of a family poem for this purpose.
- The Anglo-saxons did this a lot. To the extent that a break in the pattern in a list of Kings can be taken by historains as evidence of a change in dynasty
- The Duggar family of 19 Kids and Counting, famous for their extremely conservative religious beliefs and abnormally large family (they announced child number 20 in late 2011). All of the children's names begin with their father's initial. In order of birth, there is Josh, Jana, John-David, Jill, Jessa, Jinger, Joseph, Josiah, Joy-Anna, Jedidiah, Jeremaiah, Jason, James, Justin, Jackson, Johannah, Jennifer, Jordyn-Grace, and Josie.
- The Kardashian sisters.
- Lyndon Baines Johnson, his wife Lady Bird Johnson, and daughters Lynda Bird Johnson and Luci Baines Johnson. (There is no truth to the legend that the family dog was named Little Beagle.)
- The three daughters of crown prince Willem-Alexander of the Netherlands are called Catharina-Amalia, Alexia, and Ariane. He has joked about having a triple-A status.
- Joseph Goebbels had seven children (one adopted, six biological), named Harald, Helga, Hildegard, Helmut, Holdine, Hedwig and Heidrun. Some theorized that this was a tribute to Adolf Hitler, but there's no evidence supporting that.
- Joan Crawford's four adopted children: Christina, Christopher (originally named Phillip Terry, jr. after her then-husband when they adopted him; she had him renamed Christopher Crawford after they divorced), and identical twins Cindy and Cathy.
- Kings George I, II, III, and IV, who all ruled one after the other.
- D&D's most famous vampire, Strahd von Zarovich, had younger brothers named Sturm and Sergei.
- The Duval dynasty of Elite 2: Frontier and Elite 3: Frontier First Encounters has all emperors' names starting with H.
- The Winstrate family from Pokémon Ruby and Sapphire all have names that originate from the word "victory." Victor, Vicky, Victoria, Vito, and Vivi.
- Every named member of the Fey family in Ace Attorney except for Pearl, Ami, Iris, or Dahlia has a name beginning with an "M" (Mia, Maya, Misty, Morgan).
- In Electric Wonderland, Natasha Wing and her parents, Nathaniel and Nina Wing, all have names that begin with N.
- Pete's family in Goof Troop, Pete, Peg, PJ, and Pistol.
- The Powerpuff Girls were named because of this. Professor named Blossom and Bubbles because of their personalities. He named Buttercup because it also starts with a B.
- Alana, Adella, Aquata, Attina, Arista, Andrina, and Ariel from The Little Mermaid.
- The Jetsons all have names that start with the "j" sound, except Elroy.
- Popeye's nephews Peepeye, Pupeye, Pipeye and Poopeye.
- Definitely drew the short straw on that last one.
- Misery's family in Ruby Gloom all have names which are gloomy or negative words starting with the letter M. In the episode "Misery Loves Company" we meet her cousins Malady and Malaise. Later we get Morose and Mayhem. Misery is also a common name down the family line, so much so that they lost count of just how many have had the name.