Useful web site
FAMILY ESTIMATOR (scroll down)
http://www.ukcs.net/genes/
I used my mother's grandfather as an example and came up with this
estimate, which is not far off. The link at the bottom is to a page with
a tool called a Family Data
Sheet Estimator. It's based on mathematical models of genealogical
records dating back to 1400. These are just estimates and things 'out
of the norm' will throw it off.
Family Data Sheet Estimator
Family Member: Hughes, George M.
Husband Birth: Abt 1838 Husband Death: Abt 1904
Marriage: Abt 1862
Wife Birth: Abt 1840 Wife Death: Abt 1906
Child 1:B: Abt 1863M: Abt 1886D: Abt 1929Age 8: Abt 1871
Child 2:B: Abt 1864M: Abt 1887D: Abt 1930Age 8: Abt 1872
Child 3:B: Abt 1866M: Abt 1889D: Abt 1932Age 8: Abt 1874
Child 4:B: Abt 1868M: Abt 1891D: Abt 1934Age 8: Abt 1876
Child 5:B: Abt 1870M: Abt 1893D: Abt 1936Age 8: Abt 1878
Child 6:B: Abt 1872M: Abt 1895D: Abt 1938Age 8: Abt 1880
Child 7:B: Abt 1874M: Abt 1897D: Abt 1940Age 8: Abt 1882
Child 8:B: Abt 1876M: Abt 1899D: Abt 1942Age 8: Abt 1884
Child 9:B: Abt 1878M: Abt 1901D: Abt 1944Age 8: Abt 1886
Child 10:B: Abt 1880M: Abt 1903D: Abt 1946Age 8: Abt 1888
Estimated Children in the family: 5
The data on this sheet is only an estimate. It is for the end of lines
where you have one date and one name, it will give you a point in time to
start looking ± 8 yrs. It uses mathematical models to predict the average
family. It takes into account that medicine has improved so has the human
life span. It can not take into account war, plague, illegitimate
children, early birth, accidental death or divorce.