He was the husband of Mary, daughter of Thomas Foote, Lord Mayor of London in 1649, who had been created a Baronet in 1660 (a title which became extinct on his death in 1687).

Lord Onslow was succeeded according to the special remainder by his second cousin and heir male of his great-grandfather, who became the fourth Baron.

In May 1776, five months before succeeding in the barony of Onslow, he was raised to the Peerage of Great Britain in his own right as Baron Cranley, of Imber Court in the County of Surrey.

A grandson, André George Louis Onslow (1784–1853), was a noted composer, and author of thirty string quartets and other works.

He served in the Conservative administrations of Winston Churchill, Anthony Eden and Harold Macmillan as Captain of the Yeomen of the Guard (Deputy Chief Whip in the House of Lords) for nine years.

Upon his death on 14 May 2011,[4] he was succeeded by his son, now the eighth Earl, who inherited Clandon Park, the 1000-acre agricultural Parkland Estate in Surrey in January 2017.

Although Clandon House and gardens were gifted and endowed by the Onslow family to the National Trust in 1955, the surrounding agricultural estate called Clandon Park, covering over 1,000 acres and including areas of Grade II-listed parkland, remains in the ownership of The Earl and Countess of Onslow.

[5] The coat of arms is the basis of the badge of Onslow St Audreys School in Hatfield, Hertfordshire.

The heir presumptive is his father's fourth cousin, Anthony Ernest Edward Onslow (born 1955), a descendant of the 2nd Earl.