Once the most promising of the smaller houses in Westeros, House Tyrell has officially gone extinct. After losing its heirs, Queen Margaery, Lord Mace, and Ser Loras, only the matriarch, Olenna Tyrell, remains. Knowing her bloodline is nearly extinct, Olenna allies with the Martells and later with the Greyjoys to support the claim of Daenerys Targaryen against the Lannisters who killed her family.
When the Tarlys betray the remaining Tyrells, their seat at Highgarden is sacked by Lannister forces, led by Jaime Lannister. Before her death, however, Olenna gets one final revenge on the Lannisters: she reveals to Jaime that she was the one who poisoned his son Joffrey and requests that he tell Cersei as well. If there are any surviving Tyrells, they would be very distant cousins who have never been mentioned or seen in the series.