Oberyn Martell, also known as the Red Viper of Dorne, is the second prince of House Martell in the HBO series Game of Thrones based on the fantasy novels written by George R.R. Martin. Oberyn is known for his skill in combat, his masterful knowledge of poisons, and his sexual appetites.
Oberyn was the younger brother of Prince Doran and Princess Elia Martell and had a very close relationship with both of them. When Elia was brutally butchered along with her children by one of the Lannister’s bannermen, Oberyn struggled with her loss and held a lasting resentment toward House Lannister.
With a background that included training from the Citadel and the Second Sons, it’s no wonder he was given the moniker "The Red Viper of Dorne" to accompany his unique fighting style. He fathered eight bastard daughters called the Sand Snakes, four of them with his paramour Ellaria Sand — in this case, a “paramour” is a noble’s unmarried lover, acknowledged and respected in Dornish culture. Even though Oberyn was very open about his sexuality, he always put her first and did not shun her or hide her from the public, much to the chagrin of many of the other lords of the Seven Kingdoms. He was a family man and showed a refreshing devotion to his siblings, his children, and Ellaria.
Oberyn arrived at King’s Landing for Prince Joffrey’s wedding instead of his elder brother Prince Doran, so right off the bat, his arrival ruffled some feathers. In true Oberyn fashion, he showed up hours before he was expected so he could spend some time in one of the local brothels. We see that Ellaria is bi as well when she selects a female companion for herself, then Oberyn requests their male host instead of a woman. He never admits he is bi on the show; although, when asked later about his preferences, he said,
Then everyone is missing half the world’s pleasure. The gods made [women]… and it delights me. The gods made [men]… and it delights me. When it comes to war, I fight for Dorne. When it comes to love — I don’t choose sides.