Translated Harada's comments regarding Sicily and Xenolith's designs. Many thanks to Taiga and Jen for the scans!
Sicily
For Laharl's younger sister, since she became somewhat Pleinair-like when she was drawn as is, various changes were made. The color of her hair matches that of her mother's.
Xenolith
For Etna's older brother, his appearance doesn't hide that [they are siblings] too much. Initially, he wore a white coat, which made them seem more different, but, since the impression wasn't right, I settled with his current appearance in the end.
Sicily
For Laharl's younger sister, since she became somewhat Pleinair-like when she was drawn as is, various changes were made. The color of her hair matches that of her mother's.
Xenolith
For Etna's older brother, his appearance doesn't hide that [they are siblings] too much. Initially, he wore a white coat, which made them seem more different, but, since the impression wasn't right, I settled with his current appearance in the end.