If ancestry was destiny, we'd never have today's saint, since he suffered from extremely unfortunate ancestors. Francis was the illegitimate great-grandson of Pope Alexander VI of unfortunate memory, as well as the illegitimate grandson of King Ferdinand of Aragon. For all of Pope Alexander's many faults, he did not abandon his children, but acknowledged them and assured that they were securely placed in life, so he gave to Francis' grandfather his son the Duchy of Gandia.
So Francis grew up as a Spanish nobleman and heir. He loved learning, and received a quite creditable education, which he put to good use as a royal courtier. Eventually, he inherited the title from his father, and lived as a ordinarily upright and conventionally pious duke. He was successful in court politics, married a lady of the court, and had eight children. As Duke, he founded a university and several colleges, and imported Jesuits and Dominicans to run them.
Due to a series of personal reverses, including the death of his wife, he experienced a conversion, and became much more serious about his spiritual life, not that he was at all impious before. After concluding all of his outstanding political affairs, and seeing to the future provision of his children, he yielded his noble title to his heir and entered the Society of Jesus, where, besides growing in holiness, he eventually became the third General of the Society. Establishing the Jesuit missions in the Americas, and instrumental in regulating the internal functioning of the Society, he is often called the second founder of the Society.
So, ancestry and genetics are not all there is; they are very minor next to the graces and mercies of God.