Rico was born a "normal" human, as far as I know. But when he was a child his body started transforming, until he turned into what is commonly referred to as a "demi-human" -- something Krelian later calls the "higher" form of humanity, or it's evolved form. His mother doesn't last long after that, and from there he somehow ends up as the "Battling Champion" of Kislev's D Block.
Clothing size: extra large
Shoe size: 32cm
Ring size: 28
Rico remained the Battle Champion for years. Although he didn't have to remain in D Block, he chose to of his own free will, refusing to join Kislev's military. He and his 'associates' initiate all newcomers into the Block and it's way of life with their "baptismal ceremony" - a tournament-like fight that determines the new pecking order. They forced Fei thorugh such a ceremony when he was stuck in Kislev, and although Fei lost the first time, he won later during the gear tournaments.
At first Rico refused to help Fei, even when Dominia's task force was threatening his city. But when Elly and Fei put their lives on the line for him and the city he detested, he finally acted and joined them in their effort to prevent Dominia from completing her mission. After this, he joins the party as a permanent member.
As you may have gathered from the game, both in Rico's dreams, and in the Kaiser's palace, Rico is the Kaiser's only son. But even though his father is also of slightly demi-human heritage (an assumption of mine), he has rejected Rico, and refuses to even acknowledge him as an existing being, aside from the Gear Battling.
The reason for this is unknown. Rico's mother was killed by riots in Nortune, but no reason was given on why she and Rico were exiled in the first place -- he appeared to be completely human until he was about six or eight years old.
He is also Animus, though the Gazel Ministry did not attempt to use him the way they did the others. He was slated for death, according to the records in Krelian's lab.
Rico's scent: Samourai by Alain Delon. "...Very unique and masculine scent...Elegance, with hints of great power..."