Pinestar first appeared in Bluestar's Prophecy as leader of ThunderClan at the time Bluekit was born. He was an old and wise warrior on his last life. He did not want to lose his remaining life and so he retired to be a kittypet to live out the remaining days of his life. His deputy Sunfall became leader after him.
It is unknown what happen to him in his kittypet days. It is unknown who adopted him or how long he lived before he died.
Pinestar was able to join StarClan. Bluestar was surpised to see him as one of the cats who gave her one of her lives.