From A Wiki of Ice and Fire
The Sand Snakes are the infamous bastard daughters of Prince Oberyn Martell by various women the name alluding to their father's nickname, “the Red Viper”, and to their surname Sand, given to bastards in Dorne. Some daughters of his were born of septas, others of noble women and others still of prostitutes. Despite the variances in their birthmothers and appearances, they are all said to have their father's eyes.
Eight sand snakes, in order of age:
- Obara Sand. Daughter of a whore of Oldtown, and given to martial pursuits as she considers herself a warrior, wielding a spear and whip. She is a sturdily built woman of swarthy coloring and no particular beauty.
- Nymeria Sand. Called 'Lady Nym', her mother was a noblewoman from Old Volantis. Nymeria is elegant, refined, and beautiful with dark eyes and silky black hair worn in a braid bound with copper wires.
- Tyene Sand. Daughter of a septa. Tyene is closest of all the Sand Snakes to her cousin Arianne. She is known to have skills in herbcraft and poison, and is regarded as treacherous, while maintaining a sweet and pious persona. She is fair, blue-eyed and blonde.
- Sarella Sand. Daughter of a trader from the Summer Isles. She is referred to as playing a "game" in Oldtown.
- Elia Sand, called 'Lady Lance'. The oldest daughter of Oberyn's paramour Ellaria Sand and granddaughter of Lord Harmen Uller. She appears to have been named after Princess Elia. She's fond of horses and jousting.
- Obella Sand. Daughter of Ellaria Sand and granddaughter of Lord Harmen Uller.
- Dorea Sand. Daughter of Ellaria Sand and granddaughter of Lord Harmen Uller.
- Loreza Sand. Daughter of Ellaria Sand and granddaughter of Lord Harmen Uller.
After the death of their father by Ser Gregor Clegane, the oldest of the Sand Snakes, Obara, Nymeria and Tyene, began to pressure Doran Martell to declare war in retribution, and became involved in various plots to effect the same, including agitating the Dornish populace. Concerned that their efforts would undermine his own schemes, Prince Doran had the oldest ones confined to tower cells in Sunspear, with the exception of Sarella, who was in Oldtown. The youngest four, however, were isolated in the Water Gardens with their mother, to prevent them from being used in the plots of others and drawing Dorne into a war.