The Joker has killed Thomas Wayne in specific comic iterations. This plot twist adds depth and complexity to the characters' relationships and the overall narrative.
In certain comic arcs, Thomas Wayne is shown to be the father of the Joker. However, comic universes can vary greatly, and this isn't a universal truth for every Joker-related story.
In certain comic arcs, the idea that Joker is Thomas Wayne's son is explored. This twist adds a complex layer to their relationship and the overall narrative of the comic universe.