@Vann So it goes:

Demon's Souls

Dark Souls
Dark Souls DLC
Dark Souls: Prepare to Die Edition (Steam)

Dark Souls 2 (Steam)
Dark Souls 2 DLC
Dark Souls 2: Scholar of the First Sin (Steam)

Bloodborne
Bloodborne DLC

Dark Souls 3 (Steam)
Dark Souls 3 DLC

Dark Souls 1 Remastered

The Mysterious Game That the Devs Made a Teaser Trailer For That We Know Nothing About, But Will Probably Be Related To Dark Souls In Some Way

...in release order. Hope that clears things up!

(Edit: Forgot about the new ones. Whoops)