Their father, Henry Custis, had emigrated to Rotterdam in the Netherlands from Gloucester County in England to escape the English Civil Wars, and operated a tavern catering to fellow emigrants, as well as engaged in commerce.
His elder sister Ann married Argoll Yeardley, the son of Sir George Yeardley, who twice served as Governor of the Virginia Colony, where Sir George died in 1627.
She died before 1692 in what had become Accomack County (likewise in Virginia's Eastern Shore), after giving with to three sons (none of whom survived to adulthood) and a daughter, Joanna Mary Custis.
[2] Custis also filed indentures for several native American boys, as did fellow large landowners.
[3] In 1670 William Custis became one of the four justices of the new Accomack County Court, together with Thomas Rydings, Daniel Jenifer and Thomas Brown, who thereby joined Southey Littleton, Charles Scarburgh, Edmund Bowman and John Wise who administered the county as well as handled trials.