It’s strange Superman was ever straight to begin with

He hails from the alien planet Krypton, and thus could be anything, within or without our understanding. But by sheer coincidence, Krypton just happens to be peopled with heterosexual bipeds that look remarkably like hotter versions of Earthlings, and Superman maps closely to the traditional American ideal of what the ultimate man should be. That’s always been his deal — or the deal we gave him — and, indeed, it still is. As far as we know, the space alien named Kal-El and known as Clark Kent is still straight by default. His son, however, is bi.