Regulus as Anastasia, no one could find him because he wasn’t a princess anymore, he was a prince, well, he never knew he was a prince because Rasputin killed his family, and he lost his memory and he lived in an orphanage until 18. The only thing he had left from his family was a necklace ‘together, in Paris’
little did he know that it was his older brother, the only other survivor from the attack, who had given the necklace to him. He was in Paris, and has been looking for his sweet little sister from since he was little and brought to France from Russia. And when James potter and Remus lupin (Dimitri and Vlad) stumble upon Regulus they stare at him, shocked at how much he looked like the lost princess. So they take him in, and he tells them at some point that he was a boy but born a woman etc. James and Remus teach him how to be a proper prince, and take him to Sirius in Paris. At first they do this for the money, but slowly James and Regulus fall in love. When they went to see Sirius at the opera, Sirius didn’t believe them because he had a little sister, not brother. But when regulus explains and shows him the necklace, Sirius believes him. And, who else would have those sparkling grey eyes of his sister- or, brother? Remus falls in love with Sirius and they all live happily ever after!
also ‘learn to do it’ is so regulus because what do you mean regulus didn’t ride horseback at three and terrorized the cook??