Gizmo_Duck
blathering blatherskite!
Those From Software games are treated even by fans as if they're all in the same series hence the name Soulsborne. They just made up a name to tie them together because technically they aren't the same IP but they also aren't that far apart.
Its because they are made by the same person. Just like how Death Stranding and Metal gear share a lot of similarities/mechanics
They are fundamentally different games that aim to do different things, hence them being different IP