Early on in my family history conversations, a relative told me that my great-grandmother came from a very large number of siblings - about 21 (see Miss, Mrs, Mrs). No-one could tell me who they all were but over the decades, as I became more experienced and as extra sources of information became accessible, I added more of her brothers and sisters to my list.
In the 1881 census my great-grandmother age 16 was at home with an older sister age 21 and their parents William Moore age 75 and Elizabeth age 60. 10 years earlier, in the previous census, William age 65 and Elizabeth age 49 also had 3 older children at home, making a total of 4 daughters and 1 son. Back another decade and there are 2 further sons at home, age 14 and 16 at that time. So that gets us to 7 children - a long way from the rumoured 21 siblings.
When I found the 1851 census record, the older children whom I had seen before were present and between the ages of 2 and 9 years with their parents William age 46 and Elizabeth age 29. With them was a son called Charles age 17. Great - I had found an extra person to count towards my target of 21 siblings.
However, Charles was only 12 years younger than his mother, presumably his step-mother. Now the 15 year age gap between husband and wife made more sense. With the running total of 8 children in the family, I knew it was worth looking for an earlier wife and children for William.
The 1841 census showed Charles age 7 and a younger brother age 6 as well as an older sister and older brother. The addition of these 3 to the family tree brought the total up to 11 siblings from William and his wives.
At this point, I had found half of the family and been through all of the census years from William's lifetime.