Christiania, also known as Freetown Christiania, is Denmark's hippie-like son. (His mother is unknown, assuming he even has one - Denmark himself emerged from a sand castle, so who knows what avenues of reproduction are available to him?) A pot-smoking slacker of a micronation, Christiania believes he should be treated as a full-fledged country despite his youth, but the more he insists upon his independence, the more bratty and undeserving of it he comes across.
Christiania and Denmark demonstrate little in the way of familial affection. Equally stubborn, quick-tempered and immature, they are prone to ferocious rows. Denmark doesn't approve of Christiania's marijuana usage and general laziness, and Christiania doesn't approve of Denmark's relationship with Sister Australia, believing that she's only interested in Denmark's money. Scania is Christiania's half-brother, but presumably neither of them knows it.
Christiania hasn't interacted much with the rest of the characters, but he has had a run-in with his fellow micronation Sealand, who had offered to keep him company. In reply, Christiania cussed him out and then insulted him, which caused Sealand to run crying to England. He has also met Japan, although as he was stoned at the time he may not remember it.
Christiania is depicted as a child of indeterminate age. Denmark thinks he is about 13, but he acts much younger, jumping on beds for fun and throwing tantrums when he doesn't get his way. He has long, shaggy, sandy blond hair and wears khaki shorts, yellow shoes, and a tee-shirt colored like the flag of Freetown Christiania. (Interestingly enough, Denmark was seen wearing this very same shirt design in the strip's debut.)