Kagamine Rin / Kagamine Len / Adachi Rei / Kaai Yuki
I like to view the six Crypton Vocaloids as one big family. That said, how I see their relationships can vary depending on the work.
My favorite Cryptonloids are the Kagamines!
The first Rin song that got me into Vocaloid was Kokoro, and for Len, it was the Aku no Taizai (Evillious Chronicles) series.
What I truly cherish is the kind of platonic bond that transcends different works and settings. That unique connection between them—whether they are portrayed as family, friends, lovers, siblings, rivals, or anything else—is something I deeply respect and appreciate.
However, as officially stated, they are not strictly defined as siblings.
Their relationship is intentionally fluid—meant to free creators, not restrict them.
Personally, I like to see them as twin stars with a family-like bond.