What separated Royal Sun Elves from Sun Elves in Lyravel's society were two things - the first was legitimacy of birth, and the second was an acceptably slender, properly Noble physique.  Without these traits - even with two Royal Sun Elf parents - the child does not inherit this legal status.

The freckled, bespectacled redhead before you was one such example, and left as soon as she was old enough to realize that her future entailed several centuries of library work and quiet derision and mockery for her physique behind her shapely backside.

Surely her life here on Sinfar will be much more enjoyable...