no one knows but i think the answers is in the story of the clans came to be ya know. the cat who were dead said we will watch you from silverplet from now on those cats i think founded it.
I don't think any cat founded it. Every cat that died from the start of the journey from the mountains just became part of StarClan when they died. So there is no official founder, but Thunder, Tall Shadow, Wind Runner, and River Ripple are probably treated with the highest respect because they founded the Clans. (I'm excluding SkyClan because after they moved, they went to their own StarClan). ~ Gingerheart