Why does other KAITO's fans are a bit different from the others?

KAITO's fans can't get enough of him that the fans made god knows how many fanmade KAITOs, The Shion Family, and they're shipping the KAITOs in pjsk (Kaitocest)... And I love this fan base so much :D . 

I also am a big fan of KAITO even though I dont have many merch, and I love shipping him with the other sekai versions of him. Also I think the other Shions are pretty creative too (yes I think they're creative.), I really love these fanmade characters. But Im wondering why does other vocaloids doesn't have any other versions of themselves like KAITO so; 

• Any ideas on why is KAITO the only vocaloid who has the most popular fanmade characters and Sekai ships?