"Norman Birkett, The life of Lord Birkett of Ulverston" by H. Montgomery Hyde, pub Hamish Hamilton 1964, gives some family details; He was born William Norman Birkett, Sept 6th 1883 at 4 Ainsworth St, Ulverston in Furness and married Ruth Nilsson in 1920. As you say his father Thomas was a draper (b 1854 Haverthwaite, d 1913) Thomas married Agnes Tyson in 1877 and they had Edith, Gilbert,William Norman and Ellen (Nellie). Agnes died in 1887 and Thomas married Ann Agnes Dodding in 1888. Thomas was the son of Matthew Birkett of Haverthwaite and Agnes Carradus. My husbands Great-Grandfather George Birkett was born in Ulverston around 1852 and I have thought there might be some connection to Norman Birkett's family but as yet I've found no trace of George's birth or parents.