|Book||The World of Ice & Fire (mentioned)|
Ser Robert succeeded his father, Ser Osmund Tyrell, as High Steward. He continued his father's work in aiding his king, Mern VI, in the reconstruction of the Reach after the Dornish raid that had sacked Highgarden and killed the senile old king, Garth X.
King Mern VI was so pleased with the Tyrells that he gave Robert the hand of his youngest daughter in marriage, thereby allowing the following generations of Tyrells to claim descent from Garth Greenhand. Robert was succeeded by his son, Lorent.