Relatives!

Here we'll see who Kuja's relatives are! There are spoilers here by the way!

Zidane

At the end of disc 3, we've found out Kuja is Zidane's older 'brother'. Kuja was the first Angel of Death, but Garland thought he was a 'defect', that's why he created Zidane, who was the perfect new Angel of Death. He could start his plan this way. However, Kuja was jealous and got rid of Zidane to dump him on Gaia, thinking he was dead. He obviously wasn't.

Garland

Garland is the one who created both Kuja and Zidane. He wanted to use them to start the 'assimulation'. His plan to restore the once destoyed Terra. Garland is the closest thing Kuja has as a 'father'. Although I guess Kuja really hates him. But in some ways, they are kind of similiar. Kuja treated the Black Mages (his creations) the same as Garland did to him.

Mikoto

Mikoto is the third Angel of Death, Kuja's and Zidane's younger 'sister'. She's created for a back-up plan may Kuja and Zidane fail. She may seem as soulless as the rest of the genomes, but she isn't. There isn't much known of her.

Vivi

Although Vivi can't be really considered as 'family' I still add him. Why? Kuja was the one who created the Black Mages - and Vivi is one of them. You could say Vivi is Kuja's 'son'. (But on the other hand, Kuja would have many children O.o). Anyway, that's the main reason I add him. Kuja and Vivi don't really have a relationship. Vivi hates Kuja, and Kuja thinks Vivi is a 'defect'. In that case, Vivi and Kuja are kind of similiar.