Viscount Sydney (an alternative spelling of the surname Sidney) is a title that has been created twice.
[1] On 14 May 1694, he was also created Earl of Romney[1] but his titles became extinct when he died unmarried in 1704.
The second creation came in 1789 when Thomas Townshend (the then Baron Sydney) was made Viscount Sydney, of St Leonards, in the Peerage of Great Britain.
He served as Home Secretary and Leader of the House of Lords.
Townshend was also a female-line great-great-grandson of Lady Lucy Sydney, daughter of Robert Sydney, 2nd Earl of Leicester, hence his choice of title.