Martian Siblings

Utopia is the princess of Mars, and Elysium is her brother. Their names are rough translations of the meaning of their Martian names, which would otherwise be very difficult for any human to pronounce.
Utopia was the first-born of the emperor of Mars, and therefore the heir to the throne. Elysium is jealous of her, but he tries to keep it a secret as much as he can. On Mars, the heir to the throne must learn self-defense, history, and politics. She/he must wear battle armor to special occasions. Any other children of the emperor are allowed to study whatever they want; in Elysium's case, science.
Only males have full heads of hair on Mars. Sort of like how only male lions have manes.
Martians typically wear little clothing, since they are used to the extremely cold conditions on Mars and are rather lax about nudity in their cultures.