The only child of King Kenneth, III (1934-1992) and Queen Isolde (b. 1934), King Oisín was born in Sliabh Rook in Caisbaile, during a time of relative peace between Naranthia and the Dappled Forest. In 1965, an attack on a farm along the north-eastern border of the Dappled Forest by Naranthian elves (according to sources from inside the kingdom, which are heavily disputed by modern scholars) led to the start of the Noble War, a decade-long conflict resulting in the deaths of hundreds of Seelie fae and elves alike.
Oisín was too young to participate in the political and military planning during the first three years of the war, but often found descriptions of the reasons for the war to be confusing and unconvincing. When he got older, near the end of the war, he did more research into the causes, and began creating secret connections with Naranthian elves and fae outside the Dappled Forest, which hadn’t been done for many decades. The battles associated with the Noble War ended in 1975, though there was no formal peace treaty signed, and the Dappled Forest heightened border security, withdrawing further from international life, and even banning entry and exit between other Seelie fae kingdoms for many years.
In March 1976, while on a walk in the gardens of Sliabh Rook, Oisín was introduced to the lady-in-waiting of a local noblewoman, a young woman named Virila Barasho. The two immediately became friends, bonding over a love of books and an interest in history. Three months later, when the king and queen suggested Oisín start looking amongst the noblewomen of the Dappled Forest for a wife, he instead suggested marrying Virila. His parents were initially hesitant, but eventually approved the union, with the royal wedding between then Crown Prince Oisín and Virila Barasho occurring on 11 October of the same year. The two then moved to Spring House in the Southeastern Dappled Forest, where they lived until the death of King Kenneth in 1992.
In 1998, King Oisín was planning to pass the throne to his son, Cedar (b.1984), due to the fact that his two daughters, Iris (b. 1978) and Chrysanthemum (b. 1980) did not seem fit for the role. Upon learning this, Chrysanthemum conspired with other members of the Floral Court to depose her father, formally removing him from the throne and putting herself in his place. Oisín has not been seen or heard from since, and is suspected to have died.