I posted this on /r/fantheories and thought I should also post here.
One of the biggest mysteries in the dark souls universe is the identity of Ocelotte, the invisible child of dragons that King Oceiros holds in his arms.
There are plenty of theories out there but I have yet to see this one: Church-Spear Shira is Ocelotte.
Evidence: When we are confronted by Shira in the Ash Desert, she appears out of thin air (as if invisible) and tells us she is the daughter of the Duke and has royal blood of the gods.
Let's break that down. The only duke in the series is Seath the Scaleless, she has royal blood, which means he mated with a god of Anor Londo. The only known female god of Anor Londo (and goddess of fertility) is Gwynevere so she is most definitely the mother. So how does this mean Shira is Ocelotte?
Well we pretty much know Gwynevere became Queen of Lothric sometime after she abandoned Anor Londo (this is pretty much confirmed by in game lore descriptions, especially in TRC) and her king was Oceiros. Oceiros essentially became a prodigy of Seath; through his obsession with Seath's magics and studies, Oceiros morphed into a scaleless dragon much akin to Seath. So Gwynevere and Oceiros have a child and that child is born of dragons and has the royal blood.
Now when we enter The Ringed City, it is far in the future so Shira has grown up from being known as Ocelotte.
One last piece of evidence is the Mad-Kings Crucifix; the item description says Shira had to impale an undying Mad-king upon the spear, but he did not die, she then retreated to the dark-room. If you look closely, the body looks very sinewy and grey, much like Oceiros. Oceiros is also known as the Mad-king…
TL;DR Shira is Ocelotte; the invisible dragon child of Oceiros and Gwynevere.
Edit: if I made an error about item descriptions please let me know, I often misread things or am confusing two different items so please let me know!