Most fans may never know it, but DC's premiere superhero Batman should really be considered Jewish. It comes as no surprise since the early comic book industry was dominated by Jewish creators, channeling their own experiences of pain and persecution into some of the most memorable comic book characters of all time. Superman was created by Joe Shuster and Jerry Siegel, Stan Lee (born Stanley Martin Lieber) is celebrated for creating many Marvel superheroes, and Batman creators Bill Finger and Bob Kane (born Robert Kahn) were also Jewish.
For all that's the case, though, there are surprisingly few Jewish superheroes. At first glance, Batman himself appears to be a lapsed Episcopalian. Timelines where Bruce Wayne has died typically see him buried beneath a cross, and in Batman #53 (2018) Bruce Wayne talked about his father's Christian faith. It's a faith that Bruce doesn't share, simply because he's unable to find a satisfying answer to the question of why a loving God would stand by and watch as a young boy lost his parents. But to dismiss all issues of faith in his family as a result means overlooking it in other corners of his extended family.
For all he was brought up as a Christian, Bruce Wayne is clearly of Jewish heritage. This is actually established through his cousin Kate Kane, aka Batwoman, who numbers among those few Jewish superheroes. That's even true in the Arrowverse; the latest episode of Batwoman saw Kate refer to her bat mitzvah ceremony. Crucially, Kate is Jewish by patrilineal descent; her father Jacob is Jewish. And that logically means that his sister, Martha Kane, was also Jewish - even if she did marry an Episcopalian, Thomas Wayne.
The Jewish Law of Return stipulates that someone is a Jew if they have a Jewish mother, or they have converted to Judaism and are not a member of another religion. This is in accordance with the Mishnah, which declares that the status of a child born of a mixed marriage should be determined matrilineally. It's important to note that, as far as Jewish teachings and law are concerned, a person born a Jew does not lose that status if they cease to practice the Jewish faith, or indeed if they observe another religion, or even if they are an atheist. So while Bruce Wayne was brought up as a Christian, Jewish Law states he should really be considered a Jew by birth.
This offers a fascinating window into the complexity of Batman's character; and yet, it's worth noting that this seems to have been retconned into Batman's personal history almost by accident, rather than by intent. What's more, there's no evidence that Batman's Jewish background has ever shaped his character at all. That doesn't mean a future writer can't choose to explore that story with total validity in terms of the comic canon.
But while Batman may technically be Jewish, he certainly shouldn't be celebrated as the same highly visible example of representation as his cousin Kate.