Peregrine Bertie (the Vice Chamberlain to King William III and to Queen Anne, Teller of the Exchequer), Hon.

George Berkeley and second daughter John Massingberd, Treasurer of the East India Company), he had an elder half-sister, Lady Arabella Bertie (second wife Thomas Savage, 3rd Earl Rivers).

He was rewarded with the chancellorship of the Duchy of Lancaster in 1689, a post which enabled him to secure a seat at Preston at the general election of 1690.

[3] In 1715, he employed Sir John Vanbrugh to design a baroque front to his house at Grimsthorpe to celebrate his ennoblement as first Duke of Ancaster and Kesteven.

[3][7] This was in addition to the London mansion, Lindsey House, at 59-60 Lincoln's Inn Fields, built for the Bertie family in 1640.

[8] On 30 July 1678, Lord Willoughby married Mary Wynn (d. 1689), a Welsh heiress and direct descendant of the princely house of Aberffraw.

[6] Through his son Lord Montagu, he was a grandfather of Augusta Bertie, who married John Fane, 9th Earl of Westmorland.