I found a Fisken family in Stamfordham, Northumberland in 1861,
William aged 45, a Presbyterian Minister, his unmarried sister Margaret aged 50 and a niece Flora Fisken aged 20.
William and Margaret born in Scotland.
FamilySearch has the baptism of Margaret with parents Thomas and Elizabeth (Gray). They also have a son William baptized 18th September 1812, which fits with the census ages.
In 1871 they are still in the same place, joined by another brother David, whose baptism can also be found on FamilySearch son ofThomas and Elizabeth.
Bev.