Katherine Manners, 19th Baroness de Ros (died ~1649) was the daughter and heir of the 18th Baron de Ros. The title of Baron de Ros (pronounced Roose) is the most ancient baronial title in the Peerage of England. ...

Katherine married George Villiers, 1st Duke of Buckingham and was the mother of George Villiers, 2nd Duke of Buckingham (who inherited her title as 20th Baron de Ros). George Villiers (August 28, 1592 - August 23, 1628) was the 1st Duke of Buckingham of the second creation (1623) of that title and a favourite of King James I of England and then of Charles I. He was born in Brooksby, Leicestershire, the son of the minor noble Sir George... George Villiers, 2nd Duke of Buckingham (January 10, 1628 - April 16, 1687), English statesman, son of the 1st Duke of the second creation (1623) of that title. ... The title of Baron de Ros (pronounced Roose) is the most ancient baronial title in the Peerage of England. ...

After Katherine's first husband, George Villiers (1st Duke) was murdered in 1628 by John Fenton, she married Randal McDonnell in 1635, 2nd Earl of Antrim, and went to live at Dunluce Castle, County Antrim. Francis Manners Rutland, 6th Earl of Rutland (1578-1632), was an English nobleman. ... The title of Baron de Ros (pronounced Roose) is the most ancient baronial title in the Peerage of England. ... George Villiers, 2nd Duke of Buckingham (January 10, 1628 - April 16, 1687), English statesman, son of the 1st Duke of the second creation (1623) of that title. ...

Following the Catholic uprising in Ulster in 1641 the McDonnell family moved south to Wexford, then Waterford, where Katherine died in 1649. Katherine was known as the richest woman in Britain, apart from royalty.