On the other hand, I just found something odd while looking for Heather's Janet Anderson in the 1861. There is a Janet Anderson whose spouse is Janet Anderson. One of the Janets is male and the other female

There are children as well as a brother in the household. I think this is probably a case of reading Janet's name twice. Either the person or machine who read the census read the wrong line or, as I have seen before, the actual census taker wrote the same name twice but left the other details intact. Surely it was a machine, however, that then went on to list the father and mother as Janet and Janet for the children...! Here is the reference if anyone can take a look at the original:
Eastwood, Pollokshaws, Renfrewshire
Address: 39 Main Street
ED: 4
Page 2
Household Schedule No. 10
Roll: CSSCT1861_75
Janet Anderson, Age 28, Relationship: head, Gender: male, Spouse's name: Janet, Where born: Aberdour, Fifeshire, Occupation: Freestone (a rolling stone gathers no moss?!)
Janet Anderson, Age 27, Relationship: wife, Gender female, Spouse's name Janet, Where born: Pollokshaws, Renfrewshire
George Anderson, Age 10, Relationship: brother, Gender: male. Where born: Aberdour, Fifeshire, Occupation: joiner
Mary Anderson, Age: 5, Relationship: Daughter, Father's name: Janet, Mother's name: Janet, Gender: female, Where born: Pollokshaws, Renfrewshire, Occupation: Schooler
Elizabeth Anderson, Age 3, Relationship: Daughter, Father's name: Janet, Mother's name: Janet, Gender: female, Where born: Pollokshaws, Renfrewshire
William Anderson, Age 11 Mo, Relationship: son, Father's name: Janet, Mother's name: Janet, Gender: male, Where born: Pollokshaws, Renfrewshire