Intersex is an umbrella term used to describe people born with physical, hormonal, reproductive, ect, traits that don't fit into the typical strict male or female traits. In some cases, but not all as it varies, some individuals may develop health conditions. Intersex individuals usually have their Chromosomes, Hormones, Reproductive Systems, and uh .... Privates affected by being born Intersex, no matter what Chromosomes they are born with, usually. Even though differences ARE there, some traits might not be noticeable until puberty, some traits may never be noticeable, and some are noticeable at birth. Regarding Chromosomes in Intersex individuals, they are typically born with unique sets of Chromosomes that don't fit in the typically XX and XY. In Vanilla's case, he was born with XX/XY Chimerism and True Hermaphrodite, which is considerably rare. This means they appear male, however, they have both male and female reproductive systems/parts. This could increase the risk of infection and possible fertility disruptions. Chimerism is usually caused when two fertilized eggs fuse during verry early pregnancy.
I avoided using the medical terms for some things, as they're called "Disorders", which is offensive to Intersex individuals. I also avoided going into too much depth, y'know. https://my.clevelandclinic.org/health/articles/16324-intersex https://www.purina.co.uk/find-a-pet/articles/cat-types/breed-guides/chimera-cats https://pmc.ncbi.nlm.nih.gov/articles/PMC3271121/ https://interactadvocates.org/intersex-definitions/
