That is pretty neat, Julia.
About 10 years ago, my father gave me similar news, that I had a cousin I never knew about. Turns out his sister got pregnant 'way back, and gave the the child up for adoption. A year or so after my dad's sister died, he found an internet request from my cousin for information about his birth mother. It was too late for him to meet his mother, but he did get to meet his uncle (my father) and (the old) me and my brothers.
It was kind of cool, because we didn't have much in the way of living relatives. As soon as I saw his face, I recognized the family resemblance. He lives on a different continent, so he hasn't met the new me, but we are on Facebook and he and his wife are good with my transition.