When King James II, a Catholic, had a son in 1688 after 15 years of marriage to his second wife, the Protestant leaders in Parliament feared he would establish a new line of succession - and in the meantime, he might ally England with the Catholic leaders of Spain and France in new wars on the continent. [In the 1600's, there was no separation of church and state, and European alliances were based in part on one's religion as well as greed, hunger for power, family grudges, etc.]
Callous as it sounds, the Protestants went shopping for a replacement ruler. Closest in the hereditary line of succession was Mary, the oldest child of James II from his first wife. Mary had married Prince William of Orange (in the Netherlands) and was a staunch Protestant. With the support of English leaders, their invasion of England in 1688 turned into the Glorious Revolution when James II fled rather than fight.
William and Mary ruled together for six years until her death in 1694. King William then ruled alone until he died in 1702. Parliament increased its authority at the expense of the monarchy during their rule. The Glorious Revolution is celebrated now as a key turning point in English history, leading to the limited monarchy of today rather than rule by the "divine right of kings."
King and Queen County was formed in 1691, as was Princess Anne. It had been 22 years since the last county was formed (Middlesex), and in that time the Virginia colonies had experienced their own civil war in Bacon's Rebellion of 1676. In 1693 a college at Williamsburg was chartered.
The College of William and Mary is generally considered to be the second oldest university in British North America, after Harvard (chartered 1636), but this ignores the 10,000-acre commitment to a university at Henrico in 1619. The native American uprising in 1622 and the loss of the university's endowment in a failed iron-making venture, plus the revocation of the charter for the Virginia Company of London in 1624, brought an end to that initiative...