Who is often described as the father of tragedy?

I am not a number., Look it up. Enlighten the rest of us.

I'm confused now. In some articles, Thespis is described as the "inventor of tragedy" but others say Aeschylus was the "father of tragedy". Thespis predates Aeschylus. There are two opposing questions in Quizzland, so I got this wrong. Oh well.