I've found an interesting one here - on the Hislop clan again
OK........
Thomas and Sarah Hislop had quite a few children - one of them being Katie Hislop born 30 Aug 1890. She appears on the 1891 census with the rest of the family, as Kate - fine
Then ages ago the 1901 census, I eventually found Kate Hislop in the City Poorhouse, she was the age and birth location I was looking for and I couldn't find her with any of the rest of the family so I assumed she was the Kate I was looking for.
Meanwhile - I discovered Sarah Hislop (Kates mum), had upped sticks, leaving her husband, and moved in with another Thomas this time McLean.
She took two of the Hislop children with her, and had a further two with Mr McLean.
I found them on the 1901 census living in Edinburgh, all under the new name of McLean, and as I expected, no Kate - believing she was in the Glasgow City Poorhouse (checked the records by the way and can't find who put her in).
Then .................. when I was trawling other family members I found Rose Wright (Sarah Hislop/McLean's mother) on the 1901 census with her second husband, William Wright (although they didn't marry until 5.9.1913), and with them is a "Kate McLean" born 1890 in Hamilton, Lanark. She is stated as Williams step grand-daughter, which again is accurate.
I can't find any other Kate Hislops born around 1901 in Hamilton who the first one maybe - so is it possible that Kate appeared on the same census twice?