Jariten, known to everyone as "Ten," is Lum's little cousin. Ten is a bratty and smart-mouthed alien toddler. Like all oni, Ten possesses his own powers—he can fly and breathe fire. However, being an inexperienced child, his flying is awkward and slow, and his fire-breathing isn't always effective.
Ten may be a child, but he doesn't act his age. He exhibits a level of adult intelligence that is quite shocking for someone still in diapers. One result of his precociousness is that Ten only has eyes for older women. Despite this, he remains essentially a child and quite naive. Around women, he usually acts cute and diminutive. When he's near men, he reverts to his usual self—loud, pesky, and often aggressive.
Ten came to Earth to meet Lum's new husband but was disappointed by what he found. From the moment they met, Ataru and Ten have been at each other's throats. Because Ataru is such an idiot, Ten believes he doesn't deserve Lum. Therefore, Ten decides to live with them to keep an eye on Ataru.
(info from Furinkan.com)
