This shrine is a safe space of my comfort ship.
!!!Both characters are seen as adults. I don't ship their Anime versions.!!!
This ship is not canon and everything here is purely for entertainment purposes.
Background image by そうの•むら
Is this ship yaoi/slash?
Short answer: It depends.
In translations and localizations Kirby is adressed as a boy. But in Japan he doesn't have an official gender.
Despite his gender being officially neutral/ambiguous Kirby is sometimes adressed as かれ (kare) which is a masculine third person pronoun. Still, his gender is mostly "up to the player". Which explains why is common to see Kirby portrayed as a girl by the Japanese fandom since it's a valid interpretation of the character's gender.
But there's like a consensus to see Kirby as gender neutral and HAL doesn't mind portraying him both feminine-leaning and masculine-leaning.
As a little fun fact. Meta Knight also doesn't have an official gender in Japan!
Are they related?
There is no official information about them being related in any way beyond "probably being of the same species". Because yes, not even that is confirmed. (But it's heavily implied).
Any type of relationship between them as siblings, parent-child, lovers or mentor-student are headcanons created by the community without any confirmation from the devs.
Of course, in the context of shipping, they are not seen as family members of any type.
Isn't Kirby a kid?
Short answer: Kirby doesn't have an official canon age.
In the Japanese manuals, since the first game Kirby has been referred as "a young traveller". The word for young specifically being wakamono (若者). This word can be use to adress any person who is, as you guess, young. This mean it can be like anything from a kid to a young adult.
If you Google search the word you will mostly see pictures of late teens and young adults since it's mostly used with those age groups.
Since the term is so broad seeing Kirby as a small kid, a teen or a young adult are all correct and valid portraits of his age.
In the context of this ship Kirby is seen and portrayed exclusively as a young adult.
But in the anime Kirby was a baby
The anime, just like the light novels, even if they are official they follow a different canon from the games. Meaning there are a lot of elements and characters from the anime that don't exist in the games. You can even see a list of the differences here.
But the anime is it's own thing and it should be treated as an AU.
As a side note some games include elements from the anime. These games are seen as "collaboration" or crossover games. The prime examples are Mass Attack and Epic Yarn.
I do not ship their anime counterparts.
In the anime Meta Knight is a grown adult while Kirby is just a mere toddler. There's nothing to discuss about it.
Names and tags
List of the many names and tags used to call this ship on the Internet.
Art created by me.
MetaKirby Week 2023
A list of some official merch featuring both Kirby and Meta Knight exclusively or as part of a matching set.
Hoshi no Kirby 25th Anniversary - Pu pu Premium ring
Released in 2017 and manufactered by Ensky. Both rings were made of silver and, in the case of the Kirby one, pink gold.
Kirby set's by Twincree
In 2017 Twincree released a collection of Traditional Japanese related items featuring both Kirby and Meta Knight
Acrylic jigsaw puzzle
Released in 2015 by Ensky. These are matching puzzles since they look as being part of the same picture.
October 9 is considered to be MetaKirby day. Why? Because it's their middle birthday.
It is mostly celebrated on Twitter by the Japanese userbase.
For that they use the hashtag #10月9日はメタカビ祭
Starting from this year (2023) Metakirby will be having a ship week. A ship week is very similar to a ship day, but as its name indicates, it lasts 7 days. All week.