Board Thread:Off-Topic Discussion/@comment-6433273-20171231161124/@comment-53539-20180212164223

Technically Zero-G called Lola and Leon "soul siblings" though not confirmedif they meant brother/sister.

I'd say next would be the Kagamines but all things backtracked on them.

Officially, the first pair of true sisters in Vocaloid was Macne Nana and Petit, and their family included their elder sisters the Coco twins and a father Papa. Though not vocalodis back then, their still technically the first family.

Some of the "little sister" ideas don't mean they are related by blood/family though and only in a sort of series.