His parents believed that the priesthood was his 'destiny'. [=that he would or should become a priest because fate or God intended it]
They were living in a time when expansion to the Pacific was regarded by many people as the 'Manifest Destiny' of the United States.
She felt that 'destiny' [='fate'] had decided that she would one day be President.
(..) That sounds most excellent. A man named Stannis Baratheon was anointed as the chosen one by one of your priestesses. He, too, had a glorious destiny. He attacked King's Landing and was soundly defeated by the man standing beside me. Last I had heard, he had been defeated again, (..)2016 TvShow: Game of Thrones Title: The Door Season: 6 Episode 5