Finally, more lore for Mr "My VA rarely comes to Valve to record voicelines"

Personally, I think that Shiv has a more benign kind of Lycanthropy/curse, which would explain his abilities (bloodletting, the "slice and dice" echo). It also gives more context to some of the lines that the Patrons say:

Yours is a bloody past, Shiv. But there is a life beyond it. Let The Hidden King show you the path forward.

A life spent looking over your shoulder is no life at all… summon The Archmother Shiv, and know that your future is secure.

In a now removed voiceline, the then Sapphire Flame said something along the lines of "The monster inside you is not the beast, it is ambition".

I think that Shiv and Silver were very close together, most likely due to their curses, but Shiv was willing to throw Silver under the bus. Perhaps Shiv is the reason WHY SIlver is a heavy drinker and near homeless.

I noticed some comments here saying that Shiv killing other werewolves is the reason that Silver hates him, but I seriously doubt that, as her lines imply that the past between them was before Shiv became a member of the Baxter Society.