[1] He was the son of Edward Grimston, by his wife Anne, daughter of John Garnish (Garneys) of Kenton, Suffolk.
His grandfather was Edward Grimston (d. 19 March 1494), a son of the diplomat Edward Grimston (d. 1478), subject of the well-known portrait of 1446 by Petrus Christus (on long-term loan to the National Gallery from his descendant the Earl of Verulam), and his second wife Mary Drury.
In 1557 he purchased from the crown the manor of Rishangles, Suffolk, subject to the life estate of Robert Chichester.
He cut his beard with a pair of scissors supplied by his servant, managed to pass for a Scot, and got to England about the middle of November.
[2] / Grimston surrendered himself to the indictment against him, and was confined, first in Sir John Mason's house, and then in the Tower of London.
His son, Edward Grimston, by his first wife, married Joan, daughter of Thomas Risby of Lavenham, Suffolk, and granddaughter of John Harbottle of Crossfield, and died in 1610.