Rosanna M. Tremayne (nee Birkbeck, of that landed family, b. 1974), wife of Michael W. Tremayne, gave birth to a son, Benjamin William, 31 March, 2006, a brother for Emily Rose, who was b. 15 July, 2004.
Michael is the elder son of Mr and Mrs John Tremayne, of Easton Grey, Wiltshire, and Rosanna is the younger daughter of Mr John Oliver Charles Birkbeck, [b. 1936], of Litcham Hall, Kings Lynn, Norfolk, by his wife, the former Hermione Anne Dawes.
Rosanna Tremayne is a granddaughter paternally of Colonel Oliver Birkbeck [1893-1952], by his wife, the former Lady [Wilhelmina] Joan Mary FitzClarence, sister of the 5th Earl of Munster.
The infant is therefore a great-great-great-great-great-grandson of King William IV and Mrs Jordan.
Source: Daily Telegraph 4 Apr 2006