Rickon Baratheon was the only son of King Harys Baratheon and heir to the Iron Throne. He was killed at the age of 8 while a ward at the Water Gardens in Sunspear.
When the Lannisters sacked the capital, Rickon was taken hostage. He was flayed by Lord Varyo Velaryon at the command of King Damon Lannister in order to force action from his father, King Harys Baratheon.
Rickon was sent to be warded at the Water Gardens in Sunspear under Princess Sarella Martell as part of the Dornish negotiations following the war. Months later, he was killed in an "accident" orchestrated by Lord Rymar Royce, Master of Whisperers for the Iron Throne.
Harys Baratheon, father
Gianna Martell, mother
Joseph Baratheon, uncle
Cleos Baratheon, uncle
Aryyn Martell, uncle
Sarella Martell, cousin