I was raised Jewish (not Christian) by my grandmother, my mother's mother, who lived with us when I was growing up. She had many Jewish customs and insisted her mother was totally Jewish, so I have always known I am a Jew, but now, it turns out, not in the way I had thought. Turns out, it was my grandmother's "wicked" stepmother (Nannie) who was Jewish --the one who raised her, not her birth mother who died when she was four years old.
Nannie was not well regarded by the family. They said she was mean and mistreated my grandmother. But if this were true, then why did my grandmother feel so connected to her? I suspect, therefore, the real reason my mother's family didn't get along with Nannie was because she had insisted on maintaining a Jewish home.
This means, of course, that I am not a Jew by birth, but it hasn't changed the fact that I am Jewish, and I'm no less Jewish than I was before I learned of it. Which may not be Jewish enough by some standards --I have much to learn, I'm sure.