When your mother asked for your sister, who before today was the only girl the queen and former king ever had, it didn't seem strange to you. No, your thoughts on the subject was that your mother didn't want you to be weirded out by your new body more than necessary, and having a family member help you rather than a servant might help in that regard. After all, if dragons could use their magic to take on human shape, it was only as a reinterpretation of their natural body. In simpler terms, you couldn't take on your old, male appearance.
Then you see a young maid come with the promised cloths in her hands. "Here are the garments you asked for, your majesties" say the servant, expertly bowing while holding out the cloths to your mother. She somehow seem familiar to you, and so does her voice, but you suppose she must have been a former attendant of your sister who displeased her one way or another and got retrograded to simple maid as punishment.
Your mother take said clothes in her own hands before saying. "You can drop the disguise, we're alone." And before your dumbfounded eyes, you see some sort of illusion being dissipating, revealing the maid to be none other than your sister, princess Faith DeLaFoie.
"Wha?!? Bu… Bu…" is your intelligent answer.
"That, sister, is linked to the secret of us, female members of the royal family. A secret inherited from the First Queen of our country, and that no male of our family know."
"Only the Dragon King, our forefather, was told" pursued your mother. "You remember how I said it was his love that prevented him from turning evil?"
"Are you saying his wife didn't love him back?"
"Not when he married her, no. You see, he met the person who would become the First Queen during a diplomatic visit far in the east. She was someone far below his station, a servant the local lord had assigned to him for his stay, a commoner. But it didn't stop him from falling in love for her."
"But while she was a commoner, she was far from a banal one. Neither the future Dragon King or the east lord she worked for knew it, but she was a member of a ninja clan. What is a ninja? Try to imagine a spy and a hitman all rolled in one. Usually, ninjas are under the service of a lord, spying and, if the need arise, killing, to protect their master's interest. But it wasn't the case of this clan."
"No, our First Queen was a member of a independent clan, which infiltrated, manipulated and sometime even killed the every noble house they entered in contact with. Their main goal was to stay independent, but becoming the hidden masters of the world was another of their known objectives. As such, they indoctrinated their kids since birth so they were utterly loyal to the clan, to the point they would kill the person they most cared for if asked, without hesitation."
"So our forefather might only have been the king of a little, unimportant city-state, it was a golden opportunity for her clan to obtain a foothold in the west. So she was ordered to play the love-stuck girl and convince by any means the lord she was infiltrating to let her go. It ended with the king paying a financial compensation to the lord of the east for taking away one of his servant."
"At first, the new queen stayed loyal to her clan, but as you may know, dragons are matriarchal creatures. So while he already asked for his wife's opinion a lot before his change, after it, she literally was the one to have the last word on every decision. Somehow, having so much powers made her fall in love for real.
… And that's when she betrayed her clan."
"She got back to them, only to massacre almost all members. Only the kids too young to have the slightest memory of what happened were spared. She took said children back with her and, at her return, revealed the truth to her husband. After which she used her clan's very method to ensure said kids would grow as loyal servants who would do anything for the good of the kingdom, and did the same with her daughters, but made sure none of her sons would be aware of it."
"To this day, most of our servants are descendants of those children, and all of them were raised the same way as their forefathers. As we were, us, girls of the royal family. So turn to your human form, put on those clothes, and come with us, so we can start your reeducation."