In fourth grade, we watched Anastasia, and one of our teachers told us that while much of the story was fantasy, the family really was killed and that the "oldest child was only 13" (of course, in reality, it was the youngest!). I was obsessed with the movie and shortly after, checked out Anastasia's Album from the library and fell in love with the story of the Romanovs. My knowledge of 19th and 20th century royals was pretty huge, but at the time, I didn't really know much about other royal families aside from the British one (and only, as someone elsewhere in the thread mentioned, about the Queen, Charles, Diana, William and Harry). I remember lugging around the almost 700-page long A Lifelong Passion in middle school and reading it whenever I got a chance in class. I was even a member of an alternate history Romanov role-playing forum, which I actually think may still be active to this day, though I haven't posted there in ages.
My dad is our family historian and thanks to him, I discovered a love for geneaology, and in particular, royal geneaology. I wish I could show y'all how many files I have on my computer from when I made family trees of Queen Victoria's descendants. I'm about 20% of the way through porting my information over to Ancestry and putting it in tree form there as well. I don't know why but it's such a fun hobby for me. Probably most of middle and early high school, I was more interested in the older royals, starting with the Victoria era royals, and then Tudors, Valois, Bourbons, etc. I read a ton of those Royal Diaries books in elementary and middle school, which led to reading Jean Plaidy and other historical fiction authors. Definitely went through a Ptolemaic and Ancient Egypt period.
I became interested in modern royals in 2005, around the time of Christian of Denmark's birth. I was a member of the Alexander Palace Time Machine forums and I remember it being mentioned on there. Then, I discovered a whole world of modern royals and spent a love of time at the Royal Forums. Amazingly, I still remember Christian's birth was even mentioned as an AP blurb in the international column of my local newspaper! I actually wrote congratulations letters to both Fred & Mary, and Felipe & Letizia on the births of their babies. I got a lovely card from Fred and Mary and a paper telegram from Felipe and Letizia, but unfortunately, they both got lost and probably thrown out moving to and from my dorms or apartments in college