From the 1901 England census
183 Osmaston Road, Derby (St Andrew's Parish)
Isaac Brentnall, head, m, 44, Primitive Methodist miister, b Derby Wirksworth
Claudia Brentnall, wife, m, 36, b St Austell Cornwall
+6 children
Mary A Harry, Mother in Law, Widow, 65, Retired grocer, born St Austell Cornwall
Gilbert Harry, nephew, 8, b Guernsey C I
Class: RG13; Piece: 3216; Folio: 147; Page: 40.
He later served for 18 months in the Derbyshire Volunteers (like the Army Reserve) before being discharged as medically unfit. I'll be looking for this info on my next trip to the Archives at Kew.
Glen